ASME Conference Presenter Attendance Policy and Archival Proceedings

2014;():V003T00A001. doi:10.1115/IMECE2014-NS3.

This online compilation of papers from the ASME 2014 International Mechanical Engineering Congress and Exposition (IMECE2014) represents the archival version of the Conference Proceedings. According to ASME’s conference presenter attendance policy, if a paper is not presented at the Conference, the paper will not be published in the official archival Proceedings, which are registered with the Library of Congress and are submitted for abstracting and indexing. The paper also will not be published in The ASME Digital Collection and may not be cited as a published paper.

Commentary by Dr. Valentin Fuster

Biomedical and Biotechnology Engineering: Bioinspired Materials and Structures

2014;():V003T03A001. doi:10.1115/IMECE2014-36778.

Biofilms are bacterial colonies that form at interfaces, where bacteria are encased in extracellular polymeric substances (EPS). Biofilms are ubiquitous in both artificial systems and our environment. Here we focus on understanding biofilm growth within a stagnant pool of confined diluted culture of the bacteria. Sporosarcina pasteurii is taken as the model bacterium for this study. The motivation behind the choice of this organism stems from the fact that S. Pasteurii has the unique ability to precipitate calcite inside the host media which has tremendous applications in reservoir and restoration engineering. As the biofilm evolves with time inside the confinement, the dynamics of transport is recorded continuously by an optical microscope and the data processed digitally to gain valuable insights into the bio-physical aspects of the system.

Commentary by Dr. Valentin Fuster
2014;():V003T03A002. doi:10.1115/IMECE2014-38970.

The human vocal folds are subjected to complex dynamic biomechanical stimulation during phonation. The aim of the present study was to develop and evaluate an airflow-induced self-oscillating mechanical model, i.e., a bioreactor, which mimics the geometry and the mechanical microenvironment of the human vocal folds. The bioreactor consisted of two composite synthetic vocal fold replicas loaded into a custom-built airflow supplied tube. A cell-scaffold mixture was injected into cavities within the replicas. The folds were phonated using a variable speed centrifugal blower for two hours a day over a period of seven days. The static and dynamic subglottal pressures and the dynamic supraglottal pressure were monitored. A similar bioreactor without mechanical excitation was used as positive control. The cell-scaffold mixture was harvested for cell viability and collagen type I immunohistochemistry tests seven days after injection. The flow-induced self-oscillations of the vocal fold replicas were shown to produce mechanical excitations that are typical of those in the human vocal fold lamina propria during phonation. The results confirmed that human vocal fold fibroblasts survived inside the present bioreactor, and maintained cellular functions of protein production.

Commentary by Dr. Valentin Fuster
2014;():V003T03A003. doi:10.1115/IMECE2014-39125.

This paper presents initial investigation on a hybrid artificial muscle actuator combining two actuation technologies, based on conductive polymers and shape memory alloys (SMAs). Polypyrrole is used as the conductive polymer muscle and nickel-titanium as shape memory alloy to make the composite muscle system. Depending on the geometry of the actuator, doped polypyrrole exhibits large strain, consuming less voltage and current; whereas shape memory alloy generates large stress (force), consuming high power (high current). Helically wound coil structure was chosen as the shape of the composite actuator in this study. The polypyrrole is synthesized on the surface of the Ni-Ti shape memory alloy wire, wound around a core gold coated polylactide fiber (PLA). Preliminary results on the performance and synthesis conditions of the composite actuator will be presented for various applications under different conditions.

Topics: Actuators
Commentary by Dr. Valentin Fuster

Biomedical and Biotechnology Engineering: Biomechanics of Trauma due to Accident, Surgery or Weapons

2014;():V003T03A004. doi:10.1115/IMECE2014-37132.

This paper reports on a series of indentation tests performed on ballistic gelatin (10%) and Perma-Gel. In these experiments, both gels were submitted to strain rates varying from 0.1 and 2.7 s1 in quasi-static indentation. Two methods were used to evaluate the Young’s modulus from quasi-static indentation test: the Hertz theory and the Oliver-Pharr model. The dependence of strain rate was also analyzed. Finally, dynamic indentation tests were performed on both gels at frequencies of 0.1 and 1.0 Hz to evaluate the gel’s viscoelastic properties characterized by the storage modulus, the loss modulus and the phase angle.

Topics: Gelatin , Testing
Commentary by Dr. Valentin Fuster
2014;():V003T03A005. doi:10.1115/IMECE2014-37143.

Recent wars have highlighted the need to better protect dismounted soldiers against emerging blast and ballistic threats. Current helmets are designed to meet ballistic performance criterion. Therefore, ballistic performance of helmets has received a lot of attention in the literature. However, blast load transfer/mitigation has not been well understood for the helmet/foam pads. The pads between the helmet and head can not only absorb energy, but also produce more comfort to the head. The gap between the helmet and head due to the pads helps prevent or delay the contact between helmet shell and the head. However, the gap between the helmet shell and the head can produce underwash effect, where the pressure can be magnified under blast loading. In this paper, we report a numerical study to investigate the effects of foam pads on the load transmitted to the head under blast loading. The ALE module in the commercial code, LS-DYNA was used to model the interactions between fluid (air) and the structure (helmet/head assembly). The ConWep function was used to apply blast loading to the air surrounding the helmet/head. Since we mainly focus on the load transfer to the head, four major components of the head were modeled: skin, bone, cerebrospinal fluid (CSF) and brain. The foam pads in fielded helmets are made of a soft and a hard layer. We used a single layer with the averaged property to model both of those layers for computational simplicity. Sliding contact was defined between the foam pads and the helmet. A parametric study was carried out to understand the effects of material parameters and thickness of the foam pads.

Topics: Stress
Commentary by Dr. Valentin Fuster
2014;():V003T03A006. doi:10.1115/IMECE2014-38399.

The objective of this paper is to provide useful information to both military and law enforcement dynamic entry teams for estimating the level of protection provided by their standard protective equipment and procedures. The procedures investigated include: the K-Equation for predicting safe standoff, the effects of stack spacing, and the effect of the orientation of the stack within the blast field on the breachers’ blast exposure. This investigation leveraged both experimental data gathered during explosive breaching training exercises (Breacher Consortium, 2011 - draft) and numerical simulations using the shock physics code CTH (McGlaun, 1990).

The analysis revealed that the presence of objects within the blast range, including the other team members, significantly affected the individual’s exposure to the point that it sometimes exceeds current exposure recommendations. When each team member’s exposure was compared to the current limit of 4 psi (28 kPa), the average pressure from the gauges on the breacher helmets exceeded that level 43% of the time, and the averaged pressure at the shoulders exceeded the limit 50% of the time. In a comparison of the measured incident impulse energy to the maximum impulse energy predicted based on 4 psi peak pressure, the helmet impulse energy was exceeded 79% of the time and 64% of the time at the shoulders. Because the K-Equation was shown to be accurate in predicting the free-field pressure, these results and the output from the numerical simulations suggest that the stack and blanket do not provide the level of protection anticipated and that reducing the standoff distance, as prescribed by some protocols, is not justified.

Ultimately, the operational impact of these results will depend on efforts to identify blast exposure injury thresholds. Since there is a direct relationship between the peak overpressure and total impulse to which the breaching team members in the stack are exposed, injury thresholds must reveal which component, pressure, impulse or a combination is more injurious. Based on whether pressure or impulse must be minimized, the ideal stack configuration can be calculated using the developed numerical model.

Commentary by Dr. Valentin Fuster
2014;():V003T03A007. doi:10.1115/IMECE2014-38648.

Traumatic brain injury may occur in baseball due to a head impact with a thrown, pitched, or batted ball. It has been shown that the average pitching speed of youth pitchers and high school pitchers is approximately 63 mph (28 m/s) and 74 mph (33 m/s), respectively. At pitching speeds of approximately 52 mph (23 m/s), the bat exit velocity (BEV) for metal bats has been shown to be approximately 100 mph (45 m/s). Head kinematics, such as linear and angular head accelerations, are often used to establish head injury risk for head impacts. With a possible ball impact velocity reaching speeds in excess of those typically tested for baseball headgear, it is necessary to understand how the head will respond to high velocity impacts in both helmeted and non-helmeted situations. In this study, head impacts were delivered to the front and side of a Hybrid III 50th percentile male anthropomorphic test device (ATD) by a baseball traveling at speeds of 60 mph (27 m/s), 75 mph (34 m/s), and 100 mph (45 m/s). Head impacts were performed on the non-helmeted ATD head and with the ATD wearing a standard batting helmet certified in accordance with the NOCSAE standard. The Hybrid III headform was instrumented with a nine accelerometer array to measure linear accelerations of the head and determine angular accelerations. Peak resultant linear head accelerations for the non-helmeted ATD were approximately 200–400 g for frontal impacts and approximately 220–480 g for lateral impacts. Peak resultant angular head accelerations for the non-helmeted condition were approximately 17,000–32,000 rad/s2 for frontal impacts and approximately 30,000–60,000 rad/s2 for lateral impacts. For the helmeted ATD, peak resultant linear accelerations of the head were approximately 70–300 g for frontal impacts and approximately 80–360 g for lateral impacts. Peak resultant angular head accelerations for the helmeted ATD were approximately 5,000–14,000 rad/s2 for frontal impacts and approximately 7,500–30,000 rad/s2 for lateral impacts. HIC values for the non-helmeted ATD were approximately 193–1,025 for frontal impacts and approximately 241–1,588 for lateral impacts. SI values for the non-helmeted ATD were approximately 235–1,267 for frontal impacts and approximately 285–1,844 for lateral impacts. HIC values for the helmeted ATD were approximately 16–415 for frontal impacts and approximately 23–585 for lateral impacts. SI values for the helmeted ATD were approximately 25–521 for frontal impacts and approximately 32–708 for lateral impacts. In comparison to the non-helmeted condition, the results demonstrate the effectiveness of a batting helmet in mitigating head accelerations for the frontal and lateral impact conditions tested.

Commentary by Dr. Valentin Fuster
2014;():V003T03A008. doi:10.1115/IMECE2014-38874.

Animal models are commonly used to study spinal cord injuries (SCI). These models aim to better understand the traumatic behaviour of the spinal cord in vivo. However, experimental SCI models usually simulate a posterior contusion of the spinal cord on small animals, which do not reproduce completely the SCI mechanisms in humans.

The objectives of the study are: 1) to develop an experimental anterior contusion of the spinal cord on porcine models, and 2) to compare biomechanical differences between ventral and dorsal approaches.

A total of 6 specimens were tested in vivo with a drop weight bench test. Impacts were produced at T10 with 5mm diameter impactor of 50g and dropped from a height of 100mm. Compression time was set to 5min for 4 specimens (2 ventral, 2 dorsal) and 60min for 1 ventral and 1 dorsal. The outcome measures were the compression displacement, blood pressure, heart rate and macroscopic inspection of the spinal cord.

This is the first study proposing an animal model of anterior SCI. Preliminary results suggest that there is a biomechanical difference between ventral and dorsal contusion approaches. A new bench test especially designed for ventral contusion will allow additional tests analyzing more variables, such as the motor evoked potentials and arterial blood flow.

Topics: Spinal cord
Commentary by Dr. Valentin Fuster
2014;():V003T03A009. doi:10.1115/IMECE2014-38930.

An “underbody blast” (UBB) is the detonation of a mine or improvised explosive device (IED) underneath a vehicle. In recent military conflicts, the incidence of UBBs has led to severe injuries, specifically in the lower extremities The foot and ankle complex, particularly the calcaneus bone, may sustain significant damage. Despite the prevalence of calcaneal injuries, this bone’s unique properties and the progression of fracture and failure have not been adequately studied under high strain rate loading. This research discusses early efforts at creating a high-resolution computational model of the human calcaneus, with primary focus on modeling the fracture network through the complex microstructure of the bone and creating micromechanically-based constitutive models that can be used within full human body models. The ultimate goal of this ongoing research effort is to develop a micromechanics-based simulation of calcaneus fracture and fragmentation due to impact loading. With the goal of determining the basic mechanisms of stress propagation through the internal structure of the calcaneus, a two-dimensional model was employed for preliminary simulations with a plane-strain approximation. In this effort, a cadaveric calcaneus was scanned to a resolution of 55 μm using an industrial micro-computed tomography (microCT) scanner. A mid-sagittal plane slice of the scan was selected and post-processed to generate a 2D finite element mesh of the calcaneus that included marrow, trabecular bone, and cortical bone elements. The calcaneus was modeled using two-dimensional quadratic plane strain elements. A fixed boundary condition was applied to the portion of the calcaneus that, in situ, would be restrained by the talus. A displacement of 1.25 mm was applied to the heel of the calcaneus over 5 ms. In a typical result, following impact, the strain and stress are propagated throughout the cortical shell and then began to radiate into the bone into the bone along the trabeculae. Local stress concentrations can be observed in the trabecular structure in the posterior region of the bone following impact. Upon impact, cortical and trabecular bone show different stresses of 13MPa and 1 MPa, respectively, and exhibit complex high frequency responses. Observed results may offer insight into the wave interactions between the different materials comprising the calcaneus, such as impedance mismatch and refraction. Pore pressure in the marrow may be another important factor to consider in understanding stress propagation in the calcaneus.

Commentary by Dr. Valentin Fuster
2014;():V003T03A010. doi:10.1115/IMECE2014-38953.

A better understanding of the influence of material nonlinearities on the propagation of mechanical stress waves is necessary to generate insights into damage mechanisms of soft tissues subjected to rapid and strong external excitations. In this effort, the authors study the propagation of longitudinal stress waves through soft tissue. Emphasis is placed on the influence of nonlinear material behavior and nonuniform cross–section on the characteristics of the stress–wave propagation. The mechanical behavior of the soft tissue is represented by a nonlinear viscoelastic model that is obtained through a maximum dissipation, thermodynamically consistent construction. The effect of the tissue nonlinear mechanical behavior is studied through asymptotic analysis. Examining the obtained analytical approximation, it is possible to discern nonlinear wave front steepening and the effect of the material dissipation. The effects of a nonuniform cross–sectional area are investigated through numerical simulations. These studies can be applied to understand the effect of geometric features of axons on the propagation of longitudinal stress waves. For example, the diameter of an axon gradually increases near its ends, and varicosities/boutons along the axons represent concentrated cross–sectional area variations. Simulations are carried out to examine various aspects of the nonlinear wave propagation such as wave front steepening. This work can serve as a basis for better understanding the mechanical causes underlying mild traumatic brain injury caused by a head impact or explosive blast waves.

Commentary by Dr. Valentin Fuster
2014;():V003T03A011. doi:10.1115/IMECE2014-39107.

Sports-related concussion is a major public health problem in the United States that is estimated to occur in 1.6–3.8 million individuals annually, and is particularly common in football. Despite the significance and growing concerns about the potential long-term consequences of concussion, its biomechanical mechanisms are not fully understood. Since 1970’s computational head modeling has proved to be an efficient tool for establishment of health injury criteria and studies on head injury mitigation.

One important step in the computational modeling of the human head is to develop the mathematical material models (constitutive models) for the tissue. There have been many attempts to develop an accurate constitutive model for brain tissue. Recent experimental studies have highlighted the significant influence of axonal fibers on the non-linear and anisotropic behavior of brain tissue. Tractography based on diffusion tensor imaging (DTI) has been used in various previous studies to develop a constitutive model for human brain by including the anisotropic properties. Though DTI provides a macro scale information about the axonal fibers in the brain, it cannot directly describe multiple fiber orientations within a single voxel. To address this limitation within the DTI tractography, Diffusion Spectrum imaging (DSI), a variant of Diffusion Weighted Imaging, is used. DSI is generally used in deriving connectome sets and is sensitive to intravoxel heterogeneities of fiber orientation in diffusion direction caused by crossing fiber tracts and thus allowing for more accurate mapping of axonal trajectories than other diffusion methods. Thus more accurate constitutive models can be developed from the structural information about the human brain using DSI.

This paper extends, the anisotropic constitutive models developed previously, for two family of fibers which will be useful in the computational modeling of the human brain using DSI.

Commentary by Dr. Valentin Fuster
2014;():V003T03A012. doi:10.1115/IMECE2014-39174.

A number of activities subject the spinal cord [1] to various loading conditions that lead to disc degeneration. In this paper a brief overview on the understanding of the micromechanics and mechanisms of intervertebral disc degeneration is presented and extended to include water loss and disc height change. The focus is on a computational model of the intervertebral disc degeneration that attempts to capture the initiation and the progression of the damage mechanism under fatigue. This model can be used to study the effects on disc under short or long period biomechanical loading in work or combat environments.

Commentary by Dr. Valentin Fuster
2014;():V003T03A013. doi:10.1115/IMECE2014-39338.

The intrinsic complexity of the human head and brain lies within the non-uniformity of their constitutive components in terms of shape, material, function, and tolerance. Due to this complexity, the directionality of impact, when the head is exposed to an assault, is a major concern as different responses are anticipated based on the location of impact. The main objective of the study was to show that while most studies propose the injury criteria as based on the kinematical parameters, the tissue-level brain features are more substantiated injury indicators. Accordingly, a finite element (FE) approach was employed to elucidate the injury-related behavior of the head for front, back, and side impacts against a rigid wall. To this end, a 50th percentile FE head-neck model, including most anatomical features, was used. The kinematics of the head in terms of the linear acceleration, as well as the biomechanical response of the brain at the tissue level in terms of intracranial pressure (ICP) and maximum local shear stress, were evaluated as the main injury criteria. Ls-Dyna, a transient, nonlinear, and explicit FE code, was employed to carry out all the simulations. To verify the influence of impact directionality, identical boundary conditions were enforced in all impact scenarios. While brain responses showed similar patterns in all three directions, different peak values were predicted. The highest peak values for the local shear stress, ICP gradient, and the center mass linear acceleration of brain were observed for the frontal impact. These threshold values are of great significance in predicting injuries such as diffuse axonal injury (DAI) resulting from the shear deformation of brain axons. It is believed that directionality considerations could greatly help to improve the design of protective headgears which are considered to be the most effective tools in mitigating a TBI.

Topics: Brain
Commentary by Dr. Valentin Fuster

Biomedical and Biotechnology Engineering: Clinical Applications of Bioengineering

2014;():V003T03A014. doi:10.1115/IMECE2014-36166.

Multidrug resistance (MDR) occurs in prostate cancer, and this happens when the cancer cells resist chemotherapeutic drugs by pumping them out of the cells. MDR inhibitors such as cyclosporin A (CsA) can stop the pumping and enhance the drugs accumulated in the cells. The cellular drug accumulation is monitored using a microfluidic chip mounted on a single cell bioanalyzer. This equipment has been developed to measure accumulation of drugs such as doxorubicin (DOX) and fluorescently labeled paclitaxel (PTX) in single prostate cancer cells. The inhibition of drug efflux on the same prostate cell was examined in drug-sensitive and drug-resistant cells. Accumulation of these drug molecules was not found in the MDR cells, PC-3 RX-DT2R cells. Enhanced drug accumulation was observed only after treating the MDR cell in the presence of 5 μM of CsA as the MDR inhibitor. We envision this monitoring of the accumulation of fluorescent molecules (drug or fluorescent molecules), if conducted on single patient cancer cells, can provide information for clinical monitoring of patients undergoing chemotherapy in the future.

Topics: Cancer , Drugs
Commentary by Dr. Valentin Fuster
2014;():V003T03A015. doi:10.1115/IMECE2014-36556.

Biomedical imaging has played an important role in identifying and monitoring the effectiveness of the current state of the art treatments for many diseases. We recently proposed a novel holographic microwave imaging array (HMIA) technique for lesion detection. One of the most important considerations of this technique is the antenna array configuration. This paper demonstrates investigation of using various antenna array configurations to generate a high-resolution microwave image by using the HMIA technique. Both simulation and experimental results are obtained and compared using spiral, random and regularly spaced array configurations to fully demonstrate the effectiveness of antenna arrays to the HMIA technique. The results show that the proposed spiral and random array configurations have the ability to produce high-resolution images at significantly lower cost compared to regularly spaced array. The potential biomedical imaging applications of the research findings would be breast cancer detection and/or brain stroke detection.

Topics: Microwaves , Imaging
Commentary by Dr. Valentin Fuster
2014;():V003T03A016. doi:10.1115/IMECE2014-36619.

Oxygen is an essential therapeutic agent used extensively in all hospitals for patients with compromised function of the respiratory or cardiac systems. All patients (with the exception of neonates with certain heart diseases) are resuscitated with 100% oxygen. The American Heart Association Guidelines for Resuscitation state that it is essential in the post-resuscitative phase to decrease the concentration of O2 provided to keep oxyhemoglobin saturation (SpO2) > 94%, with a goal of avoiding hyperoxia while ensuring adequate oxygen delivery. Hyperoxia has been shown to be responsible for worsening tissue injury via oxidative damage following ischemia-reperfusion. Therefore, it is important in the post-resuscitative phase to use the lowest inspired oxygen concentration (FiO2) that will maintain SpO2 ≥ 94%. To address this, clinicians use oxygen blenders: devices that mix room air (21% O2) and medical grade oxygen (100% O2) to create a desirable FiO2. Current oxygen blenders have the disadvantage of being wall-mounted, bulky, and are limited to a small set of oxygen delivery devices (nebulizers, mechanical ventilators) with which they can interface. We developed an oxygen blending device capable of mixing room air and 100% O2 using the venturi principle. The device features a cylindrical body with a venturi nozzle and an entrainment window. It is handheld, portable, and machined from acrylic plastic. An oxygen blender with these features allows for appropriate oxygen therapy during patient transport. As oxygen flows through the device from the inlet orifice, atmospheric air is drawn in through the window, mixed, and then delivered to the patient through the outlet orifice. We designed the outlet orifice to have the same dimensions as the inlet orifice, allowing for universal integration with any device that connects to standard oxygen tubing. The entrainment window area can be adjusted by twisting a cover over the body of the blender, thus adjusting the FiO2 delivery. Using a venturi nozzle of 6.35 mm in diameter and an entrainment window area of 97 mm2, we achieved FiO2 ranging from 40% to 50% using input flow of 100% O2 at 6 L/min at 50 psi (via rotameter). The key feature of this device is that it can be interposed between any standard oxygen tubing allowing control of FiO2 at the bedside of the patient in hospital or during transport. Further work is needed to achieve a wider FiO2 range.

Topics: Design , Oxygen
Commentary by Dr. Valentin Fuster
2014;():V003T03A017. doi:10.1115/IMECE2014-36774.

Doctors of chiropractic (DCs) use manual palpation to subjectively assess the relative “stiffness” (resistance) of spinal articulations to help inform decisions regarding where to focus treatment. The objective of this study was to quantify the forces generated by DCs when assessing patients with low back pain (LBP). This is an observational study nested into a three-arm randomized clinical trial evaluating two forms of chiropractic treatment and one sham control. LBP patients of both genders between 21–65 years of age participated in the study. Measurements were collected with the participants lying prone on an examination table embedded with force plates. Three DCs applied manual force downward on the participants to obtain a sense of relative joint resistance over vertebral segments L1-L5, the superior sacrum, and bilateral sacroiliac (SI) joints. Peak forces generated during the manual assessments were extracted using custom-written, semi-automated, MathCad software. The results were descriptively analyzed using SPSS statistical software. Three clinicians manually assessed spinal resistance during 230 observations. Mean peak force ranged from 128–178N. Higher force levels were observed at lower vertebral levels and the pelvis by two of the clinicians. L3 and L4 spinal levels showed the greatest similarity of force applied by 3 DCs.

Commentary by Dr. Valentin Fuster
2014;():V003T03A018. doi:10.1115/IMECE2014-38152.

Cardiovascular disease is the leading cause of death worldwide. This disease includes chronic total occlusion (CTO), which is a complete blockage of an artery. Unlike partial occlusions, CTOs are difficult to cross percutaneously using conventional guidewires (thin and flexible wires) because of the fibrotic and calcified nature of the blockage. The lack of data regarding the mechanical properties of CTO limits the development of new technologies in the field of percutaneous coronary intervention (PCI) and percutaneous peripheral intervention (PPI). In this study, calcified plaques retrieved from occluded arteries are analyzed in order to better understand their mechanical properties and to help propose an artificial analogue. Calcified plaques samples were collected from the superficial femoral artery wall within one hour following a lower limb amputation surgery. These samples were studied to determine their composition and mechanical properties. The same characterization procedures were performed on various potential artificial analogues. These analogues include three plaster materials and dense hydroxyapatite blocks. The results were then compared with those of the calcified plaques in order to determine the more favorable analogue. This mechanical analysis and the proposal of a potential analogue for the calcified plaques found in occluded arteries could benefit the development of new technologies and devices in the field PCI and PPI.

Commentary by Dr. Valentin Fuster
2014;():V003T03A019. doi:10.1115/IMECE2014-38225.

The use of three-dimensional scanning techniques in the medical field has become increasingly relevant. Laser projection systems have been applied onto human skin tissue in a variety of ways, especially in navigated surgery. However, a highly accurate and portable scanning system with the ability to analyze human tissue from multiple recording directions has yet to be developed and certified as a Class I medical device. This project aims to find the ideal setup of a portable, intuitive and certified scanning system of human tissue without the need of projective equipment. The scanning tool consists of a stereo camera by Northern Digital Instruments (NDI) and an infrared laser module. This paper presents the system’s ideal parameter settings while varying its accuracy when applying a laser module with wavelength of 850nm onto human tissue.

Topics: Lasers
Commentary by Dr. Valentin Fuster
2014;():V003T03A020. doi:10.1115/IMECE2014-38388.

The life of dental implant depends on various parameters such as insertion torque, implant diameter and cortical and cancellous bones thickness. The thickness of the cortical and cancellous bones varies from patient to patient and for each thickness, the corresponding studies are required to determine the favorable implant loading. In this study, stress analysis on various dental implant fixtures inserted in compromised bony ridges is performed using three dimensional finite element analyses. Initially, the modeling and analysis of previously analyzed structure is done to validate the solution procedure. After successful validation, three dimensional linear elastic analysis of bone implant bone assembly is performed. The implant material is treated as isotropic whereas the bone materials are taken as anisotropic materials. The parametric study finds the effect of insertion torque and variation of implant diameter on stress induced in the compromised bony ridge. Further, the implant bone assembly was analyzed using various cortical bone thicknesses. It has been observed that the increase in torque results in increased stress and deformation in the bone. With increasing bone thickness, the similar variation of torque produces less stress and deformation in dental implants. The study is helpful in prediction of favorable implant loading and implants diameters for compromised bony ridges. The study provides useful knowledge in improving the performance and life of dental implants.

Commentary by Dr. Valentin Fuster
2014;():V003T03A021. doi:10.1115/IMECE2014-38995.

The physiological ratio of compression to anterior-posterior (A-P) knee joint loads has substantial effects on the loading of soft tissue structures, patellofemoral loads, and knee kinematics [1, 2]. There is also a direct relationship between resultant kinematics and joint forces. D’lima et al. was also able to compute A-P kinematics at a given flexion angle with minimal error using measured A-P and compressive load acquired from the instrumented tibia [3]. The direction of A-P load measured at the tibia is associated with the direction of translations of the femur relative to the tibia.

Topics: Kinematics , Knee
Commentary by Dr. Valentin Fuster
2014;():V003T03A022. doi:10.1115/IMECE2014-39720.

Activities of daily living include carrying objects using one hand. Carrying a load using one hand can alter the loading on the musculoskeletal system as well as the walking pattern. The objective of this pilot study was to quantify the ground reaction forces, electromyographic (EMG) activity of trunk muscles, and trunk motion during walking. Nine human volunteers with no symptoms of pain were recruited from the student and employee population of an academic institution. Data were recorded from 8 volunteer subjects. Participants were asked to walk at self-selected speed back and forth at their comfortable speed carrying loads varying from 0 to 25 pounds on right hand on a wooden walking platform for 30 steps/cycles. Motion data were recorded from T1, L1, L3, and S1 vertebrae at a sampling frequency of 120 Hz. Range of Motion (ROM), Correlation Dimension (CoD), and Approximate Entropy (ApEn) was computed using custom written MatLab programs. EMG data were recorded from six muscle groups bilaterally (right and left): Erector Spinae, Multifidus, Latissimus Dorsi, Internal Obliques, External Obliques and Rectus Abdominis at a frequency of 1200 Hz. Root mean square EMG values, Mean and Median Frequency of the EMG data were calculated to observe the effect of increasing load on muscle fatigue using custom developed MatLab program. Ground reaction force (GRF) data were collected using a force plate and the associated 1st peak force (Fz1), 2nd Peak force (Fz3) and minimum force (Fz2) between the two peak forces were calculated during gait cycle. The ROM values had a range from 2.6–3.2 deg. for Lumbar lateral bending (LB), 6.7–8.7 deg. for Thoracic LB. Approximate Entropy (ApEn) values ranged from 0.20–0.40 for Lumbar LB motion and 0.30–0.50 for Thoracic LB motion. Correlation Dimension (CoD) values ranged from 1.20–1.40 for lumbar LB and 1.20–1.30 for Thoracic LB. Normalized GRF increased during walking with increased load. Significance difference (P<0.05) were found for vGRF with increase in load. Motion and EMG data did not reveal any significant differences.

Topics: Stress , Biomechanics
Commentary by Dr. Valentin Fuster
2014;():V003T03A023. doi:10.1115/IMECE2014-39823.

Current ultrasound approaches practice probe for diagnosing instantaneous abdominal aortic aneurysms (AAA) based on arterial tissue deformation. However, tracking the progression of potential aneurysms, and predicting the risk of rupture is based on the diameter of the aneurysm and is still an insufficient method: Larger diameter aneurysms do not always lead to ruptures, and smaller diameter aneurysms unexpectedly rupture. In order to improve diagnostic accuracy of ultrasound imaging techniques, this paper presents geometric analyses of patient-specific instant deformations as a means to develop an aneurysm rupture mechanism. Segmented AAA images were used to analyze dependent elements that contribute to a three-dimensional (3-D) aneurysm reconstructive model using proposed Patient-Specific Aneurysm Rupture Predictor (P-SARP) method. The outcomes indicate that the proposed technique has the ability to associate the distortion of wall deformation with geometric analyses. This method can positively be integrated with established ultrasound techniques for improvements in the accuracy of future diagnoses of potential AAA ruptures.

Topics: Rupture , Aneurysms
Commentary by Dr. Valentin Fuster
2014;():V003T03A024. doi:10.1115/IMECE2014-39910.

Mitral regurgitation (MR) is a common consequence of ventricular remodeling in heart failure (HF) patients with systolic dysfunction and is associated with diminished survival rates. Characterization of patient-specific anatomy and function of the regurgitant mitral valve (MV) can enhance surgical decision making in terms of medical device choice and deployment strategy for minimally invasive endovascular approaches for MV repair. As a first step toward pre-operative planning for MV repair, we examine the feasibility of using cardiac magnetic resonance (CMR) images acquired in multiple orientations to resolve leaflet function and timing. In this study, MV motion of a HF patient with ischemic heart disease exhibiting both adverse ventricular remodeling and MR was compared pre-operatively against a normal control from the Sunnybrook cardiac database, starting with manually segmented 2D MV contours from cine CMR images acquired in multiple orientations. We find that MV motion analysis from CMR imaging is feasible and anatomical reconstruction using oriented segmentations from a combination of imaging slices acquired in multiple orientations can help overcome inherent limitations of CMR image data in terms of resolving small anatomical features, owing to finite slice-thicknesses and partial volume effects.

Commentary by Dr. Valentin Fuster
2014;():V003T03A025. doi:10.1115/IMECE2014-40168.

Stroke can result in Hemiparesis, often resulting in the disuse of impaired limbs and the increased use of the unimpaired limbs. Disuse leads to muscle atrophy, contracture and stiffening of the joints, which impedes daily living and quality of life. Physical therapy can maintain or increase motor function following stroke, but the impaired limb may still have less motor function than the unimpaired limb, leading to further disuse. Thus negating the gains accomplished by therapy. The development of devices that assist motor function of the impaired limbs during daily activities would promote use and help maintain any progress from physical therapy. Automated motion assistance can overcome spasticity by allowing a user to perform a specific task multiple times, thus reducing the stiffness developed in the fingers.

The purpose of this study was to develop prototype modules of a glove-like system for hand grasping assistance. The full system could be used during therapy sessions or worn to assist with activities of daily living. The force sensors positioned in the glove on the front and back of each fingertip would be used to determine whether an attempt is being made to grasp or to let go of an object. The system controls motors that wind or unwind cables that run along the forearm and connect independently to the glove for each finger. The modules were designed and assembled for testing. A simulation model was built for analysis. The early results appear promising, but further testing will be required to make developments toward the full system to assist with hand motor function.

Topics: Grasping
Commentary by Dr. Valentin Fuster
2014;():V003T03A026. doi:10.1115/IMECE2014-40225.

A nanowell sensor for single molecular proteomic analysis of lung cancer has been designed. The nanowell sensor is an electrochemical immunoassay and comprises of a heterogenous nanoporous arrays integrated on to a gold microelectronic platform. The sensor operates on the principle of electrochemical impedance spectroscopy (EIS). Our approach to classification of lung cancer is based on screening for levels of expression of specific proteomic biomarkers associated with lung cancer stem cells. Proteomic activity for two lung cancer cell lines for two specific markers (ALDH1A1 and ALDH1A3) was quantified. Test samples prepared by synthetically spiking human pooled serum were tested and quantified for cancer stem cell marker activity. The lowest proteomic activity measured with (a) ALDH1A3 was 0.01 ng/mL and (b) ALDH1A1 was 1 ng/mL correlating to the detection of unit stem cell count.

Commentary by Dr. Valentin Fuster
2014;():V003T03A027. doi:10.1115/IMECE2014-40238.

Electromyography (EMG) is a method for monitoring the electrical activity of skeletal muscles. The EMG signal is used to diagnose neuromuscular diseases and muscular injuries. EMG can also be utilized as an indicator of user intent for a muscle contraction for a specific motion. This input signal could be used to control powered exoskeleton prostheses. Limbs with impaired motor function tend to have increased disuse that may result in further muscle weakness. Therapy and other physical activities that increase the use of an impaired limb may contribute to some recovery of motor function. A device that helps to perform activities of daily living may increase usage and enhance recovery. The objective of this project is to make developments toward an EMG controlled assistive rehabilitation system that monitors EMG signals of the bicep and triceps muscles, and drives a motor to assist with arm motion. A motor is used to develop torque that would assist rotations of the arm about the elbow. A pair of EMG sensors (one pair near the biceps and the other near the triceps muscle) transmits electrical activity of the arm to a microcontroller (Raspberry Pi, Raspberry Pi Foundation, United Kingdom). For the prototype, the EMG signal is sampled and rectified within a moving time window to determine the root mean squared (VRMS) value. This value is used by the microcontroller to generate a pulse-width modulated (PWM) signal that controls the motor. Sensors for the motor provide information to an algorithm on the microcontroller. The generated PWM signal is based on the Vrms values for the EMG signal. Testing and analysis has shown a correlation between the EMG Vrms amplitude and muscle generated torque. The EMG controlled assistive rehabilitation system shows promise for assisting motor function for rotations about the elbow. Further algorithmic development is needed to determine the appropriate amount of assistance from the motor for the motor function indicated by user intent.

Commentary by Dr. Valentin Fuster
2014;():V003T03A028. doi:10.1115/IMECE2014-40337.

Breast cancer is one of the most common types of cancer among women with over 230,000 incidences diagnosed every year. A typical breast cancer surgery might include but is not limited to, biopsies, breast conservation surgery or mastectomies. Moreover, these surgeries usually cause soreness in the shoulder and arms which in turn affect the ability of the patient to perform simple everyday activities.

Lymphedema, another serious side effect of these surgeries, when coupled with radiation therapy, can appear in breast cancer patients during months or even years after the treatment ends. Lymphedema is a condition in which high-protein fluid collects beneath the skin and causes swelling, redness and discomfort. This condition occurs in breast cancer patients when lymph nodes are damaged or removed during the procedures.

Research suggests that early physiotherapy as well as exercises can reduce the risk of lymphedema. Monitoring the progress during these exercises can be a first step in diagnosing lymphedema. Along with better prognosis, the patients can observe the benefits of early diagnosis with insurance coverage, since most insurance companies do not cover treatments associated with advanced stages of lymphedema. The initial stretching workouts, done during recovery, target the range of motion of the shoulder that is affected by the surgery. This range of motion, determined by the severity of the surgery, improves over time. These exercises can then be used to drain the lymph nodes and help retain flexibility in the affected muscles. A monitoring device engineered to provide data about the extent of recovery would be a significant aide to both the patients and healthcare professionals.

The intent of the paper is to introduce a distinctive device that monitors workouts and uses the data as a motivating factor for the patient as well as an early detection system for lymphedema. The device shows the effort that the patient has put for each workout into user friendly real time graphs. Patients and healthcare professionals can then use this data and graphs to identify problem areas in the recovery process. Preliminary tests of this device, which are presented in this paper, showed promising results in accuracy and repeatability as the device calculated and displayed graphs which were a quantified estimation of the range of motion and workout effort of the user.

Topics: Cancer
Commentary by Dr. Valentin Fuster

Biomedical and Biotechnology Engineering: Computational Modeling and Device Design

2014;():V003T03A029. doi:10.1115/IMECE2014-36505.

This paper presents the research that has been undertaken into the passive humidification device cavity airflow structures and patterns. This was aiming to improve the device airflow, Heat and Moisture Exchange (HME) materials performance, for a greater patient care. However the objectives were to assist in understanding the optimal cavity structural geometries, generating improved airflow patterns over target HME material structures and consequently leading to improved heat and moisture exchange properties.

Airflow studies of the device have been undertaken using the Computational Fluid Dynamics (CFD) interface of the ANSYS. The CFD package enables analysis of fluid flow and heat transfer. This paper presents the results of the CFD simulations carried out on different passive humidification device cavity designs and materials arrangements. An optimised design leading to enhanced airflow structures and patterns, heat and moisture properties of the device is also presented in this paper.

Commentary by Dr. Valentin Fuster
2014;():V003T03A030. doi:10.1115/IMECE2014-36603.

A physics-based computational model of neonatal Developmental Dysplasia of the Hip (DDH) following treatment with the Pavlik Harness was developed to obtain muscle force contribution in order to elucidate biomechanical factors influencing the reduction of dislocated hips. Clinical observation indicates that reduction occurs in deep sleep and involves passive muscle action. Consequently, a set of five (5) adductor muscles, namely, the Adductor Brevis, Adductor Longus, Adductor Magnus, Pectineus, and Gracilis were identified as mediators of reduction using the Pavlik Harness. A Fung-type model was used to characterize the hyperelastic stress-strain muscle response. Four grades (1–4) of dislocation as specified by the International Hip Dysplasia Institute (IHDI) were considered. A three-dimensional model of the pelvis-femur-lower limb assembly of a representative 10 week-old female was generated based on CT scans of a 6-month and 14-year old female as well as the visible human project with the aid of anthropomorphic scaling of anatomical landmarks.

The muscle model was calibrated to achieve equilibrium at 90° flexion and 80° abduction. The hip was computationally dislocated according to the grade under investigation, the femur was restrained to move in an envelope consistent with Pavlik Harness restraints, and the dynamic response under passive muscle action and under the effect of gravity was resolved using the ADAMS solver in Solidworks.

Results of the current model with an anteversion angle of 50° show successful reduction IHDI Grades 1–3, while IHDI Grade 4 failed to reduce with the Pavlik Harness. These results are consistent with a previous study based on a simplified anatomically-consistent synthetic model and clinical reports of very low success of the Pavlik Harness for Grade 4. However, our model indicates that it is possible to achieve reduction of Grade 4 dislocation by hyperflexion. This finding is consistent with clinical procedures that utilize hyperflexion to help achieve reduction for patients with severe levels of DDH for whom the Pavlik Harness fails.

Commentary by Dr. Valentin Fuster
2014;():V003T03A031. doi:10.1115/IMECE2014-36699.

Low magnitude, high frequency whole-body vibration (WBV) has been found to increase bone mineral density in both animal and clinical studies [1,2,3]. The mechanism behind this phenomenon is unknown and a model would be beneficial to assist in analyzing the effects of WBV on the human skeleton. In this paper, Kane’s method is used to find the equations of motion for a multi-body model of the human body standing on a vibration platform [4]. The model consists of nine rigid bodies connected by ideal joints that simulate the skeletal structure of the human body. Spring and damper elements represent the ligaments and tendons connecting the rigid bodies; a sinusoidal force function denotes the vibration input of the platform. This model is lumped, assuming no relative motion between the feet and the vibration platform. The equations of motion generated by Kane’s method are solved in MATLAB using fourth-order Runge-Kutta. The results from the simulation were compared to experimental data in order to validate the model.

Topics: Vibration
Commentary by Dr. Valentin Fuster
2014;():V003T03A032. doi:10.1115/IMECE2014-36860.

This paper presents an automatic simulation procedure to study the stump-socket interaction that has been embedded within a software platform specifically developed to design lower limb prosthesis. In particular, it investigates and compares the results obtained by means of FE tools with the experimental data acquired with pressure transducers. A transfemoral (amputation above knee) male amputee has been considered as case study. Numerical simulations have been carried out considering different techniques to acquire the residuum geometry and different socket models. In details, two residuum geometric models were reconstructed starting from MRI images and from 3D scanning to investigate how acquisition techniques influence the final results. Two socket geometric models were taken into account. The first was the patient’s real socket, acquired by 3D scanning; the second one has been modeled using a dedicated CAD system, named Socket Modeling Assistant. The patient’s real socket has been also used to perform the experimental pressure measurements. The experimental data have been acquired by means of the Tekscan F-socket system. Results reached so far allowed identifying main criticalities and future developments to improve the accuracy of the numerical results and make available a full-automated simulation procedure.

Commentary by Dr. Valentin Fuster
2014;():V003T03A033. doi:10.1115/IMECE2014-36947.

Ambient particulates depositions have major impacts on respiratory functions. Patient-specific simulations of the respiratory system of a patient were performed to investigate the relationship between the flow characteristics and particulate depositions in the upper respiratory domain. CT scan images were imported to create a 3D model of the bronchial tree and then transferred to a computational fluid dynamics (CFD) software for simulation. Appropriate boundary conditions were assigned to simulate the sinusoidal behavior of the normal breathing cycle with the corresponding pressures at the outlets. Lagrangian phase model was used to simulate the micron solid round particulates transport and depositions. The simulations were performed for 2.5 micron and 10 micron particles. The implicit-unsteady Reynolds Averaged Navier-Stokes equations with K-ω turbulence model were used for these simulations. Results indicate high correlation between regions of high vortices, secondary flow and high wall shear stress and particulate depositions. The total deposition number for 10-micron particles was higher than that for the 2.5-micron particles. The differences in the locations of depositions at various generations of the lung illustrate the importance of the patient-specific simulations.

Commentary by Dr. Valentin Fuster
2014;():V003T03A034. doi:10.1115/IMECE2014-37167.

Circulating tumor cells (CTCs) are metastatic cancer cells in the circulatory system. Researchers have recently realized that CTCs can serve as excellent biomarkers for early cancer detection, which can greatly increase the chances for successful follow up treatment. Among CTC detection methods, a new method called CTC-chip is promising to make future early cancer diagnosis a routine inspection. Using size effect and cell deformability, deformation-based CTC filter is reported to be an inexpensive and effective solution. Cancer cell deformation mechanism is believed to be important in CTC-chip design. Most existing CTC-chips use Young-Laplace model to describe cell deformation. However, the deformation behavior of cancer cell under high velocities is observed to be very different from the static Young-Laplace model according to our present research. In this study, we characterize the detailed cell deformation process when they are passing through CTC microfluidic channels using volume of fluids (VOF) model simulation. Our study provides valuable information for future high throughput CTC chip design.

Commentary by Dr. Valentin Fuster
2014;():V003T03A035. doi:10.1115/IMECE2014-37300.

Titanium alloy (Ti6Al4V (ASTM F-136)) is typically used for modular hip implant stems. This highly corrosion resistant alloy forms passive surface oxide films spontaneously. However, with modular designs, micro-motion may occur at the taper junctions during mechanical loading.

Complex physical/chemical reactions take place which may result in pitting and crevice corrosion. Crevices between the taper junctions may allow the body fluids to enter and remain stagnant. These conditions make the modular tapers susceptible to fatigue and mechanically assisted crevice corrosion. When two or more surfaces are in close proximity, it leads to the creation of a locally blocked region in which enhanced dissolution may occur. The in vivo degradation of metal alloy implants compromises the structural integrity.

Stochastic modeling of crevice corrosion is performed based on the mechanism behind the phenomenon. Sensitivity analysis is performed, and conclusions drawn.

Commentary by Dr. Valentin Fuster
2014;():V003T03A036. doi:10.1115/IMECE2014-37301.

Friction-induced squeaking has been reported in 1–20% of patients who have a ceramic on ceramic total hip replacement, which is a subject of annoyance. Friction induced stick-slip phenomenon is the driving force behind squeaking. Stick-slip occurs when the film lubrication is broken. Fluid film lubrication is a function of sliding speed, lubricating fluid viscosity, bearing roughness, clearance, and contact pressure. A breakdown of fluid film lubrication may result from edge loading, presence of third bodies (wear particles) during articulation, damage to the articular surface (increased roughness), mismatched bearing diameters, etc. In the present study, influence of variation in relative densities of the biofluid and femoral head is mathematically investigated when the spheres are initially subjected to an impulse (start-up condition: initial contact to pre-swing phase of the gait cycle). The parametric analysis also looks at the influence of initial impulse speed, and time of approach of the femoral head to the outer shell.

Commentary by Dr. Valentin Fuster
2014;():V003T03A037. doi:10.1115/IMECE2014-38028.

There is a growing demand for quantifying the performance and efficacy of rehabilitation programs. Researchers are advocating home based rehabilitation devices and continuous monitoring of patients status in real time through wearable sensors. This paper investigates the use of inertial measurement sensors for recording the dynamic gait status. In order to facilitate long term recording and minimal interface of recording devices, these MEMS sensors are advantageous in many ways over the conventional laboratory methods. Portable Harness Ambulatory System (PHAS) can be effectively used in home environments with minimal assistance for gait rehabilitation. This paper addresses the stages of mechatronic integration of a prototype of PHAS with an aim for early gait rehabilitation of elderly and stroke survivors without fear of falling. Sensors modules comprised of accelerometer and gyroscope were developed. X-bee wireless communication protocol is used for transmitting the gait data for computer storage. Gait experiments with wireless sensor modules attached to shoulder, wrist, thigh and ankle joints of normal human subjects were conducted for slow and fast walking speed. The inertial measurement sensors provide information on the range of motion, gait speed, and orientation. Experimental results prove that sensor modules were successfully able to acquire and record the gait information wirelessly. These sensor modules can also be integrated in the PHAS prototype. The paper outlines the results of initial research and discusses possible alternatives.

Topics: Sensors
Commentary by Dr. Valentin Fuster
2014;():V003T03A038. doi:10.1115/IMECE2014-38454.

Physiological tissue-on-a-chip technology is enabled by adapting microfluidics to create micro scale drug screening platforms that replicate the complex drug transport and reaction processes in the human liver. The ability to incorporate three-dimensional (3d) tissue models using layered fabrication approaches into devices that can be perfused with drugs offer an optimal analog of the in vivo scenario. The dynamic nature of such in vitro metabolism models demands reliable numerical tools to determine the optimum tissue fabrication process, flow, material, and geometric parameters for the most effective metabolic conversion of the perfused drug into the liver microenvironment. Thus, in this modeling-based study, the authors focus on modeling of in vitro 3d microfluidic microanalytical microorgan devices (3MD), where the human liver analog is replicated by 3d cell encapsulated alginate hydrogel based tissue-engineered constructs. These biopolymer constructs are hosted in the chamber of the 3MD device serving as walls of the microfluidic array of channels through which a fluorescent drug substrate is perfused into the microfluidic printed channel walls at a specified volumetric flow rate assuring Stokes flow conditions (Re<<1). Due to the porous nature of the hydrogel walls, a metabolized drug product is collected as an effluent stream at the outlet port. A rigorous modeling approached aimed to capture both the macro and micro scale transport phenomena is presented. Initially, the Stokes Flow Equations (free flow regime) are solved in combination with the Brinkman Equations (porous flow regime) for the laminar velocity profile and wall shear stresses in the whole shear mediated flow regime. These equations are then coupled with the Convection-Diffusion Equation to yield the drug concentration profile by incorporating a reaction term described by the Michael-Menten Kinetics model. This effectively yields a convection-diffusion–cell kinetics model (steady state and transient), where for the prescribed process and material parameters, the drug concentration profile throughout the flow channels can be predicted. A key consideration that is addressed in this paper is the effect of cell mechanotransduction, where shear stresses imposed on the encapsulated cells alter the functional ability of the liver cell enzymes to metabolize the drug. Different cases are presented, where cells are incorporated into the geometric model either as voids that experience wall shear stress (WSS) around their membrane boundaries or as solid materials, with linear elastic properties. As a last step, transient simulations are implemented showing that there exists a tradeoff with respect the drug metabolized effluent product between the shear stresses required and the residence time needed for drug diffusion.

Commentary by Dr. Valentin Fuster
2014;():V003T03A039. doi:10.1115/IMECE2014-38711.

From Ambient Assisted Living (AAL) perspective it is important to have information regarding the type of care needed by bedridden elderly people (BEP) living in their homes, in order to support independence, autonomy and maximize their quality of life. Some basic tasks as eating, taking a bath and the hygiene cares may be difficult to execute, regarding that almost always the main caregiver is the other element of the couple (husband or wife). Following this trend, the development of mechatronic devices is of upmost importance in creating solutions to facilitate these tasks. This paper presents the conceptual design of a mechatronic system especially devoted to the assistance during the bath of BEP. Issues as reducing the number of caregivers to only one to assist the bath and reducing the system’s handling complexity (because most of the time it will be used by an aged person) are considered. Visits to rehabilitation centers and hospitals, and respective working meetings, are considered in the development of the proposed mechatronic system.

Commentary by Dr. Valentin Fuster
2014;():V003T03A040. doi:10.1115/IMECE2014-38767.

The determination of head and neck biomechanics is one of the keys for deep understanding of impairments in neck function and cervical spine pathologies. Finite element models are a valuable tool to perform parametric studies. In this study, we aim to investigate the effect of a 40N head weight on the biomechanics of the head and neck complex under flexion-extension moments. The loading is applied to the centre of mass of the head and the first thoracic vertebra is fixed. Our predictions show that the kinematics and the load distribution at the facet joints were altered significantly with considering of the head weight under the flexion and extension movements. Our investigations indicate the substantial role of the head weight on the biomechanical behavior of the cervical spine and suggest its consideration in comparing the models predictions with the measurements.

Commentary by Dr. Valentin Fuster
2014;():V003T03A041. doi:10.1115/IMECE2014-39293.

The objective of this work is to characterize the interaction between balloon-expandable stents and curved artery simulants. The deformation at the outer surface of the curved artery simulant was monitored using two high-speed cameras, and the corresponding strain map was obtained with 3-D digital image correlation technique. The anisotropic variations in the arterial mechanics were clearly observed. Results indicated three distinct phases during the stenting procedure, i.e., expansion, recoil and stabilization. The stent expansion dramatically altered the strain field of the curved artery simulant, and larger strain was observed around the center of stent than its two ends. In addition, the change in curvature of the simulant during the implantation of stent was quantified. This work characterized and quantified the interaction between stent and artery simulant in a laboratory setting, which could facilitate the optimization of the stent design for minimizing the stent-induced changes in the mechanical environment of artery.

Topics: stents , Vessels
Commentary by Dr. Valentin Fuster
2014;():V003T03A042. doi:10.1115/IMECE2014-39294.

This paper presents a semi active orthosis designed for recovering the mobility on a paralyzed hand because of a fifth cervical injury, C5. The orthosis is based on a six bar mechanism and a circular slide, using the hand as a part of the mechanism. Other similar devices were developed around the world, nevertheless this design is independent of an actuator, and can be used with or without one. As a result, the mechanism and tests with the user are presented; the user of the mechanism can hold different objects with his hand using the orthosis.

Topics: Orthotics
Commentary by Dr. Valentin Fuster
2014;():V003T03A043. doi:10.1115/IMECE2014-39421.

The understanding of its shape on the movement of microparticles and nanoparticles is crucial to the development of technologies of using these particles in drug delivery systems. The effect of shape on nanoparticles used in drug delivery, in particular, is a very active area of experimental investigation. Also, the determination of the drag force on nanoparticles of different shapes is very important in designing effective nanoparticle-mediated therapies. One of the common shapes of nanoparticles is rod. In this study we present a resolved discrete particle method (RDPM), which is also called the Direct Numerical Simulation (DNS), to investigate the effect of rod shapes on the drag force in a vicious fluid as compared to other particle shapes such as a sphere and a cone. These particles are assigned the same volume and placed in contact with the bottom wall in a simple shear flow. Their drag forces are computed numerically; it is found that the particle shape has a significant effect on the drag forces. In the case of a spherical particle, our results agree very well with the analytical results found in the literature. The drag force on a rod at different orientations and the motion of two rod-shaped particles of identical volume are in a shear flow are also examined. The motion of a rod-shaped particle and a cone-shaped particle in a shear flow at low Reynolds number is also compared.

Commentary by Dr. Valentin Fuster
2014;():V003T03A044. doi:10.1115/IMECE2014-39711.

Congestive heart failure has reached epidemic proportions in developed countries afflicting an estimated 23 million patients worldwide and more than 5.7 million patients suffering from it annually in USA. Left ventricular assist devices (LVADs) have gained acceptance for non-transplant NYHA Class III & IV HF patients to provide full or partial circulatory support as a bridge to transplant or destination therapy. Recently, investigators have suggested advantages of deploying a continuous flow pump within the aorta, through transcatheter deployment (eg: Abiomed Impella pump) and an anchoring device to lodge the pump across the diameter of the ascending aorta (AAo). In this study we evaluate feasibility of such a device anchored virtually at the AAo of a patient-specific aortic arch, using computational fluid dynamics (CFD). Constant inflow rate conditions of 0.7 m/s in the axial direction with varying swirl / tangential intensity at the AAo inlet (viz. pump outlet) was modeled simulative of a range of conditions affecting aortic helical grade (viz. secondary flow), using FLUENT 14.5 (ANSYS Inc.). A change of swirl intensity from +30% (right-handed, physiological) to −30% (left-handed) swirl led to increases in peak WSS (by 10.31%) and mean WSS (by 13.04%). This simulation based pilot study indicates that WSS in transverse aortic arch is a versatile indicator of non-physiological helical flow grade and may be a promising design parameter for hemodynamics-informed aortic pump design.

Commentary by Dr. Valentin Fuster
2014;():V003T03A045. doi:10.1115/IMECE2014-39736.

In recent years, breast cancer has been a terror killer for women because of the high incidence rate. More and more researchers began to study breast cancer and made an effort to search an effective method for diagnosing breast cancer accurately. The stage achievement was reported by Li et al for AFM indentation study of breast cancer cells [1], which provided a famous method about measuring the elastic modulus to detect breast cancer. In addition, there are some common methods for the diagnosis of breast cancer, such as finger palpation, echo and mammography. However, due to the inaccuracy and pain, these methods have defects very obviously. Furthermore, it is said that palpation is most important method to reduce the mortality of the cancer in early diagnosis. However, the practical realization of the mechanical palpation system is desired since the palpation by human contains inaccuracy. Especially, three-dimensional evaluation is useful for precise diagnosis which can evaluate human body. Sakuma et al. firstly recommended Young’s modulus measurement using equivalent indentation strain in spherical indentation testing for soft flat material [2], which is also applied to evaluate the human skin successfully [3]. In this paper, three-dimensional palpation method for human body tissue based on Hertzian contact theory is proposed at first, and error reduction procedure of the method is also discussed for the improvement of identification ability of it.

Topics: Errors , Soft tissues
Commentary by Dr. Valentin Fuster
2014;():V003T03A046. doi:10.1115/IMECE2014-39743.

Approximately 55,500 proximal humeral fractures require surgical fixation annually. The current standard for internal humeral fracture fixation involves implantation of rigid metallic devices to prevent dislocation of bone fragments. However, these devices have high stiffness characteristics which can cause stress shielding in bone. A second method of fixation, called biological fixation, decreases stiffness which reduces stress shielding by utilizing more flexible devices. This approach tends leads to increased incidences of delayed healing and nonunion of fracture fragments. Therefore, this device design implements two bioabsorbable polymers in two distinct layers that degrade at different rates. The purpose of this design is to provide rigid fixation during the initial fracture healing phase followed by a period of biological fixation, allowing for functional healing along with a reduction in stress shielding over time compared to current devices. The bioabsorbable property permits the device to remain in situ, thus eliminating the need for removal surgery and reducing the risk of surgical site infection. Using finite element analysis, the design has been demonstrated to exhibit varying axial, torsional, and flexural stiffness over time. The final device was fabricated by injection molding, and tested for flexural stiffness. In addition, the polymers were tested for stiffness at specific time intervals over the course of the degradation period. All stiffness tests were performed under simple three point loads. A Nikon 3200 camera (Nikon Inc., Melville, NY) was used to sequentially image the material samples and plate throughout each load application. The flexural stiffness of the device was determined by utilizing Digital Image Correlation analysis in Matlab (MathWorks, Inc.) to analyze surface displacements between image frames. The success of the device was determined by comparing the observed difference in stiffness to standard stiffness values for humeral fixation devices currently available on the market. A substantial decrease in stiffness combines the benefits of rigid and biological fixation devices as well as eliminates the complications associated with each, providing an improved solution for proximal humeral fractures.

Commentary by Dr. Valentin Fuster
2014;():V003T03A047. doi:10.1115/IMECE2014-40070.

Total liquid ventilation (TLV) is an experimental mechanical ventilation technique where the lungs are completely filled with a perfluorocarbon liquid (PFC). It can be used to implement moderate therapeutic hypothermia (MTH) and treat severe respiratory problems. During TLV, the airway pressure must be monitored adequately to avoid overpressure and airway collapses. On the thermodynamic level, rectal, esophageal or tympanic temperature measurements are not suitable (long time constant) to avoid lowering the heart below 30°C. The objective was to design a Y connector positioned at the mouth which integrates the virtual sensors, used by controllers. The first estimates the airway pressure and the second provides the core body temperature. Pressure and RTD sensors were installed in the connector to implement the virtual measurements. In-vitro experiments were done to validate the virtual sensors. In-vivo experiments (on newborn lambs) confirm the accuracy of the airway pressure estimation and of the systemic arterial temperature.

Commentary by Dr. Valentin Fuster
2014;():V003T03A048. doi:10.1115/IMECE2014-40089.

In this study, a model of femur which resembles bone natural structure has been developed. The model initially consists of a solid shell representing cortical bone encompassing a cubical network of interconnected rods with circular cross-sections representing trabecular bone part. A computational efficient program has been developed which iteratively changes the structure of trabecular bone by keeping the local stress in the structure within a defined stress range. The stress is controlled by either enhancing existing beam elements or removing beams from the initial trabecular frame structure. Trabecular bone structure is obtained for two load cases: walking and stair climbing. The results show that as the magnitude of the loads increase, the internal structure gets denser in critical zones. The higher density is achieved using loading associated with the stair climbing. Walking which is considered as the routine daily activity, results in the less internal density in different regions of the bone. The results show that the converged bone architecture consisting of rods and plates are consistent with the natural bone morphology of femur. Furthermore, the bone volume fraction at the critical regions of the converged structure is in a good agreement with previously measured data obtained from combinations of Dual X-ray Absorptiometry (DXA) and Computed Tomography (CT).

Topics: Bone
Commentary by Dr. Valentin Fuster
2014;():V003T03A049. doi:10.1115/IMECE2014-40209.

Predicting neck response and injury resulting from motor vehicle crashes is essential for improving occupant protection, effective prevention, and in the evaluation and treatment of spinal injuries. Injury mechanism of upper cervical spine due to frontal/rear-end impacts was studied using Finite Element (FE) analyses. A FE model of ligamentous (devoid of muscles) occipito-C3 cervical spine was developed. Time and rate-dependent material laws were used for assessing bone and ligament failure. Frontal and rear-end impact loads at two rates of 5G and 10G accelerations were applied to analyze the model response in terms of stress distribution, intradiscal pressure change, and contact pressure in facet joints. Failure occurrence and initiation instants were investigated. Frontal and rear-end impacts increased stresses significantly producing failure in most components for both rates. However, transverse ligament and C2-vertebral endplate only failed under rear-end impact. No failure occurred in cortical bone, dens, disc, anterior or posterior longitudinal ligaments. The spine is more prone to injury under rear-end impact as most of the spinal components failed and failure started earlier. Ligaments and facet joints are the most vulnerable components of the upper cervical spine when subjected to frontal/rear end impacts and injury may occur at small ranges of displacement/rotation.

Commentary by Dr. Valentin Fuster
2014;():V003T03A050. doi:10.1115/IMECE2014-40231.

The spinal load sharing and mechanical stresses developed in the spine segments due to mechanical loads are dependent on the unique spinal anatomy (geometry and posture). Variation in spinal curvature alters the load sharing of the lumbar spine as well as the stiffness and stability of the passive tissues. In this paper, effects of lumbar spine curvature variation on spinal load sharing under compressive Follower Load (FL) are investigated numerically. 3D nonlinear Finite Element (FE) models of three ligamentous lumbosacral spines are developed based on personalized geometries; hypo-lordotic (Hypo-L), normal (Normal-L) and hyper-lordotic (Hyper-L) cases. Analysis of each model is performed under Follower Load and developed stress in the discs and forces in the collagen fibers are investigated.

Stresses on the discs vary in magnitude and distribution depending on the degree of lordosis. A straight hypo-lordotic spine shows stresses more equally distributed among discs while a highly curved hyper-lordotic spine has stresses concentrated at lower discs. Stresses are uniformly distributed in each disc for Hypo-L case while they are concentrated posteriorly for Hyper-L case. Also, the maximum force in collagen fibers is developed in the Hyper-L case. These differences might be clinically significant related to back pain.

Commentary by Dr. Valentin Fuster
2014;():V003T03A051. doi:10.1115/IMECE2014-40268.

Onset of valve disease, mainly stenosis, is common in post left ventricular assist device (LVAD) implantation. Hydraulically, this condition manifests itself as a change in the opening profile of the heart valve; smaller effective hydraulic diameters. Studying the onset of this disease during mock circulatory loop analysis of an LVAD design enables the cardiovascular condition changes to be more appropriately modeled. This would provide insight to the impact on changes in operating demands for a device over the course of its use; power demand and performance impact. The challenge of producing a valve that can control its opening profile to mimic both healthy and stenosis states is difficult due to the low valve differential pressures experienced in vivo (<1 psi). A novel design of a mono-leaflet swing valve that is electromechanically actuated is being developed to simulate onset of stenosis in a human aortic valve. Finite element analysis (FEA) was employed to produce a computational fluid dynamics (CFD) model of the design for the purpose of estimating the torque delivered to the actuator by the fluid flow against the leaflet. Modeling a wide range of flow rates through various valve angles of operation provided data on the full operating range for the device. Calculation of the torque on the driveshaft manipulating the leaflet angle was derived from pressure data for 38 points on the valve’s surface. Utilizing this data in a Simulink Simscape physical model of the electromechanical system enables accurate control architecture to be developed for the device through the use of design optimization. Discussion of the CFD model results and how to employ them in the Simscape model will be discussed. Performance of the physical model in a pulsatile flow study, analogous to the human circulatory system, will be presented illustrating the ability of the design to model onset of stenosis in an aortic valve.

Topics: Valves , Diseases
Commentary by Dr. Valentin Fuster

Biomedical and Biotechnology Engineering: Dynamics and Control in Biomechanical Systems

2014;():V003T03A052. doi:10.1115/IMECE2014-36909.

Up-down and rifle aiming maneuvers are common tasks employed by soldiers and athletes. The movements underlying these tasks largely determine performance success, which motivates the need for a noninvasive and portable means for movement quantification. We answer this need by exploiting body-worn and rifle-mounted miniature inertial measurement units (IMUs) for measuring torso and rifle motions during up-down and aiming tasks. The IMUs incorporate MEMS accelerometers and angular rate gyros that measure translational acceleration and angular velocity, respectively. Both sensors enable independent estimates of the orientation of the IMU and thus, the orientation of a subject’s torso and rifle. Herein, we establish the accuracy of a complementary filter which fuses these estimates for tracking torso and rifle orientation by comparing IMU-derived and motion capture-derived (MOCAP) torso pitch angles and rifle elevation and azimuthal angles during four up-down and rifle aiming trials for each of 16 subjects (64 trials total). The up-down trials consist of five maximal effort get-down-get-up cycles (from standing to lying prone back to standing), while the rifle aiming trials consist of rapidly aiming five times at two targets 15 feet from the subject and 180 degrees apart. Results reveal that this filtering technique yields warfighter torso pitch angles that remain within 0.55 degrees of MOCAP estimates and rifle elevation and azimuthal angles that remain within 0.44 and 1.26 degrees on average, respectively, for the 64 trials analyzed. We further examine potential remaining error sources and limitations of this filtering approach. These promising results point to the future use of this technology for quantifying motion in naturalistic environments. Their use may be extended to other applications (e.g., sports training and remote health monitoring) where noninvasive, inexpensive, and accurate methods for reliable orientation estimation are similarly desired.

Topics: Filters , Data fusion
Commentary by Dr. Valentin Fuster
2014;():V003T03A053. doi:10.1115/IMECE2014-36976.

The ability to move along curved paths is an essential feature for biped walkers to move around obstacles. This study is aimed at extending passive walking concept for curved walking and turning to generate more natural and effective motion. Hence three-dimensional (3D) motion of a rimless spoked-wheel, as the simplest walking model, about a general vertical fixed coordinate system has been derived. Then, two kinds of a stable passive turning, i.e. limited and circular continuous have been considered and discussed. The first kind is actually transferring from a 2D periodic motion to another, and can be implemented on a straight slope surface. While, it was shown that the second kind is just related to novel 3D periodic motions and can be recognized on a special surface profile namely “helical slope” introduced here. The latter are interpreted as 3D fixed points of a Poincare return map again. So, their stability was evaluated numerically by a Jacobian analysis and demonstrated through several simulations. Results show asymptotical stability of such motions and their considerable basin of attraction with respect to initial states. In addition, the characteristic of passive turning is shown to be strictly connected with the value of the initial perturbed condition, for instance, to the initial inclination of the wheel. It is then surprising to note that the stability of a 3D passive periodic motion (turning) is higher than 2D one (straight walking) which is actually a special case just with an infinite radius of turn.

Commentary by Dr. Valentin Fuster
2014;():V003T03A054. doi:10.1115/IMECE2014-38214.

Dynamic modeling of a biped has gained lots of attention during past few decades. While stability and energy consumption were among the first issues which were considered by researchers, nowadays achieving maximum speed and improving pattern of motion to reach that speed are the important targets in this field. Walking model of bipeds usually includes two phases, single support phase (SSP), in which only the stance foot is in contact with the ground while the opposite leg is swinging; and double support phase (DSP) in which the swing leg is in contact with the ground in addition to the rear foot. It is common in the simplified model of walking to assume the stance leg foot, flat during the entire SSP; but one may know that for human walking, there is also a sub-phase during SSP in which the heel of stance foot leaves the ground while the whole body is supported by toe link. Actually in this sub phase the stance leg foot rotates around the toe joint. This paper is trying to study the effect of toe-link and heel to toe walking model on dynamic and specially speed of walking compare to flat foot model.

Commentary by Dr. Valentin Fuster
2014;():V003T03A055. doi:10.1115/IMECE2014-38293.

This paper looks into the impact forces applied to the joints of a biped walking on an uneven surface. In this vein, impact dynamics of the swing leg are studied by considering a simple two-link planar manipulator model which comes in contact with the ground. The effect of different parameters and factors on the magnitude of the joint impact forces is investigated. Specifically, it is observed how the elasticity of the shoe, the leg configuration, and the muscular flexibility of the joints affect the joint impact forces. The obtained results can be of practical importance in developing bipedal robots and in the diagnosis and treatment of human gait issues related to joint problems.

Commentary by Dr. Valentin Fuster
2014;():V003T03A056. doi:10.1115/IMECE2014-38350.

Postural control of a standing bipedal model with toe-joints is studied. The model contains an inverted pendulum as the upper body and a foot, which consists of a heel-link and a toe-link. Taking advantage of ankle strategy, the biped is actuated by two torques at ankle-joint and toe-joint to regulate the upper body in upright position. To assess the stability of the system the Lyapunov exponents phenomena are used and the stability regions are calculated in the phase plane. To investigate the effect of toe-joint on control performance and the stability, the results are compared with those of a flat foot model without toe-joint. The relationship between heel’s height and balancing stability is investigated as well. The results show that toe-joint enhances stability of the system and reduces the actuator demand. This effect is more important especially in the case with high heel foot.

Commentary by Dr. Valentin Fuster
2014;():V003T03A057. doi:10.1115/IMECE2014-38758.

Recent development of series elastic actuators have revealed a capability to mimic muscle-like properties and achieve accurate force control. Series elastic actuators have also been widely used in humanoid and surgical robotic devices. The design of the elastic elements are critical and complex. This tends to increase costs and complexity of designing and controlling series elastic actuators. Here, we present a novel low cost and easy-to-fabricate design for a series elastic element that also has adjustable stiffness. The design consists of simple shaft couplers and spring steel plates. During the test, the stiffness of the designed elastic elements is very close to linear (R2 = 0.999) when the clamped spring-steel strip length is sufficiently long. As the clamped strip length shortens, the resulting torque deflection curve becomes slightly quadratic but remains largely linear. Also, the designed elastic element exhibits little hysteresis during loading and unloading. The stiffness of the designed elastic element can be tuned to achieve a range of stiffness values, thus it is suitable for different applications with different stiffness requirements. We also design a simple control algorithm and develop a simulation based on the dynamic properties of the designed elastic element. In simulation, the controller is able to accurately track the commanded torque values. Overall, this design could help reduce the cost and development time required for series elastic actuators.

Commentary by Dr. Valentin Fuster
2014;():V003T03A058. doi:10.1115/IMECE2014-39414.

In this paper a nonlinear human knee dynamics model to include viscoelastic ligaments is proposed. The knee model is two dimensional and include tibia, femur, ligamentous knee structure, and knee cartilages. The model is used to investigate the influence of ligamentous viscoelastic properties on dynamic testing of human knee. An exercise in which the femur is pinned at the hip in a sitting position, and tibia in a vertical position is actuated by a vertical harmonic force at various frequencies is proposed. The viscoelastic model of ligaments shows better predictions on the knee dynamic testing.

Topics: Knee
Commentary by Dr. Valentin Fuster
2014;():V003T03A059. doi:10.1115/IMECE2014-39425.

The use of apps on hand-held devices has the potential to offer advancements in controlling many devices with an intuitive user interface, including power wheelchair control. Many powered wheelchair users require special adaptations to their control interface in order to drive the chair. This paper presents the development and testing of an Android based control system for a powered wheelchair. The control system utilizes the Android device’s sensors to control the wheelchair. The device can be attached to various parts of the user’s body which the user can move to control the wheelchair. The accelerometers in the device are used to drive the chair using Bluetooth technology connected to the wheelchair’s control system. Subject testing was performed with the user holding the Android device in their hand while they performed a variety of structured tasks. These series of tasks were duplicated while the Android device was attached to their hat and again when strapped to the upper left arm. The results from the collected data on specific metrics were compared against similar data when the wheelchair is controlled using a standard wheelchair joystick.

Commentary by Dr. Valentin Fuster
2014;():V003T03A060. doi:10.1115/IMECE2014-39628.

Several control methods based on passive dynamic walking have been proposed by researchers to provide an efficient human-like biped walking robot. For most of these passive based controllers the main idea is to shape the robot’s energy level during each Single Support Phase (SSP) to restore the mechanical energy which has been lost in the previous Impact Phases (IP). In this paper, instead of controlling the energy restoration rate during each SSP, a new strategy is introduced which provides a stable walking by controlling the energy dissipation rate during each IP. Subsequently, this method is applied to an anti-trunk biped robot with lockable knee joints to realize an active dynamic walking on level ground. Simulation results show, the proposed method is effective.

Commentary by Dr. Valentin Fuster
2014;():V003T03A061. doi:10.1115/IMECE2014-39751.

The objective of this research is to evaluate the trunk kinematic data of asymptomatic human volunteers using the discrete wavelet transform. Five human volunteers with mean age of 29.6 (SD=7.4), height (m) 1.73 (SD=6.4), and weight (kg) 69.3 (SD=6.6) were recruited from the student and employee population of an academic institution. Participants were asked to walk back and forth at their comfortable speed carrying loads on one hand, on the right hand side of 0, 5, 10, 15, 20 and 25 pounds on a wooden walking platform for a maximum of 30 steps (cycles). Participants walked with self-selected speed. Motion data were recorded from T1, L1, L3, and S1 vertebrae at a frequency of 120 Hz. Three trials of data have been recorded for each participant. Using wavelet decomposition technique (five levels, Daubechies’s wavelet functions) we observed that the energy components corresponding to the levels 2, 3, 4 and 5 changed with respect of load. Comparing the no load (0 lbs) with maximum load (25 lbs), the energy of the lumbar signal decreased with 44.71% for level 2, 50.13% for level 3, 48.45 % for level 4 and 41.33 % for level 5 in average for all subjects.

Commentary by Dr. Valentin Fuster
2014;():V003T03A062. doi:10.1115/IMECE2014-39942.

The objective of this work is to develop an inverse dynamics model that uses minimal kinematic inputs to estimate the ground reaction force (GRF). The human body is modeled with 14 rigid segments and a circular ankle-foot-roll-over shape (AFROS) for the foot-ground interaction. The input kinematic data and body segment parameter estimates are obtained from literature. Optimization is used to ensure that the kinematic data satisfy the constraint that the swing leg clears the ground in the single support (SS) phase. For the SS phase, using the segment angles as the generalized degrees of freedom (DOF), the kinematic component of the GRF is expressed analytically as the summation of weighted kinematics of individual segments. The weighting functions are constants that are functions of the segment masses and center of mass distances. Using this form of the equation for GRF, it is seen that the kinematics of the upper body segments do not contribute to the vertical component GRFy in SS phase enabling the reduction of a 16-DOF 14-segment model to a 10-DOF 7-segment model. It is seen that the model can be further reduced to a 3-DOF model for GRFy estimation in the SS phase of gait. The horizontal component GRFx is computed assuming that the net GRF vector passes through the center of mass (CoM). The GRF in double support phase is assumed to change linearly from one foot to the other. The sagittal plane internal joint forces and moments acting at the ankle, knee and hip are computed using the 3-DOF model and the 10-DOF model and compared with the results from literature. An AFROS and measurements of the stance shank and thigh rotations in the sagittal plane, and of the lower trunk (or pelvis) in the frontal plane provide sufficient kinematics in an inverse dynamics model to estimate the GRF and joint reaction forces and moments. Such a model has the potential to simplify gait analysis.

Commentary by Dr. Valentin Fuster
2014;():V003T03A063. doi:10.1115/IMECE2014-40076.

The force transmission of a flexible instrument through an endoscope is deteriorated due to friction between the contacting surfaces. Friction force along the axial direction can be reduced by combining the translation motion input with rotational motion input at the proximal end of the instrument. The effect of the combined motion on the force transmission is studied for a flexible instrument through a curved rigid tube. A mathematical formula is derived for the reduction in friction force along the axial direction due to the combined motion input. The force transmission of a flexible instrument through a curved rigid tube is analysed using the capstan equation. The ratio of the input and output forces is compared for the combined motion with that of the translation motion only. A ratio ζ is defined to measure the reduction in the friction force along the axial direction due to the combined motion input. The analytical result shows the reduction in the friction force for the combined motion input. A flexible multibody model is set up and various simulations are performed with different motion inputs. The simulation result showed a reduction in the value of ζ in accordance with the analytical result for the given velocity ratio. The results are further validated with the experimental results. The simulation and experimental results show an agreement with the analytical solutions. The knowledge of force transmission with a combination of motions can be used to increase the force fidelity of a flexible instrument in applications like robotic surgery with a flexible instrument.

Topics: Instrumentation
Commentary by Dr. Valentin Fuster
2014;():V003T03A064. doi:10.1115/IMECE2014-40152.

The ability to drive a car is an important skill for individuals with a spinal cord injury to maintain a high quality of life, particularly their freedom and independence. However, driving with a physical disability often requires the installation of an adaptive driving system to control steering, gas, and braking. The two main types of adaptive driving controls are mechanical and electrical, also known as drive by wire (DBW). DBW controls work by converting electric signals to mechanical actuators. Driving simulators are useful tools for adaptive driving systems because they allow users to test different control devices, to practice driving without the dangers of being on the road, and can be used as a safe way to evaluate disabled drivers. This study focused on the development of a dynamic driving simulator using DBW controls because most studies focus on mechanical controls and not DBW controls and often use static simulators.

The simulator was developed using the Computer Assisted Rehabilitation Environment (CAREN) virtual reality system. The CAREN system (Motek Medical, Amsterdam, Netherlands) includes a six degree of freedom motion base, an optical motion capture system, a sound system, and a 180-degree projection screen. The two DBW controls, a lever device to control the gas and brake and a small wheel device to control steering, sent an electric signal to a Phidget board, which interfaced with the CAREN system. Several different driving scenarios were created and imported into CAREN’s D-Flow software. A program was developed in D-Flow to control the scene and motion of the platform appropriately based on the DBW controls via the Phidget. The CAREN system dynamically controlled the motion platform based on the user’s input. For example, if the user applied the brake suddenly, the user felt a deceleration from the motion platform moving backwards. The driving simulator showed the capability to provide dynamic feedback and, therefore, may be more realistic and beneficial than current static adaptive driving simulators. The dynamic adaptive driving simulator developed may improve driving training and performance of persons with spinal cord injuries. Future work will include testing the system with and without the dynamics from the moving platform to see how this type of feedback affects the user’s driving ability in the virtual environment.

Commentary by Dr. Valentin Fuster
2014;():V003T03A065. doi:10.1115/IMECE2014-40431.

A knee-ankle-foot orthosis (KAFO), which covers the knee, ankle and foot, can mitigate abnormal walking pattern caused by weak quadriceps. Several types of KAFOs are currently available in the market: passive KAFOs, stance-control KAFOs and dynamic KAFOs. In passive KAFOs, the knee joint keeps being locked during standing and walking, and can be unlocked manually to allow free rotation for sitting. Stance-control KAFOs (SCKAFOs) allow free knee motion during swing phase when the braced leg is unloaded. Dynamic KAFOs are able to reproduce normal walking ability throughout whole gait cycle. This research is directed at using superelastic alloys to develop a dynamic knee actuator that can be mounted on a traditional passive KAFO. The actuator stiffness can match that of a normal knee joint during the walking gait cycle. This proposed knee actuator utilizes a storing-releasing energy method to apply functional compensation to the knee joint, controlling the knee joint during both stance and swing phases. Fundamentally, the knee actuator is composed of two distinct parts which are connected with the thigh and shank segments, respectively. There are two superelastic actuators that are housed within these two parts and activated independently. Each actuator is developed by combining a superelastic rod and a rotary spring in series. When neither actuator is engaged, the knee joint is allowed to rotate freely. The stance actuator works only in the stance phase and the swing actuator is active for the swing phase. The conceptual design of the knee actuator is verified using numerical simulation and a prototype is developed through additive manufacturing for confirming the concept.

Topics: Alloys , Actuators , Knee
Commentary by Dr. Valentin Fuster

Biomedical and Biotechnology Engineering: Innovations in Processing, Characterization and Applications of Bioengineered Materials

2014;():V003T03A066. doi:10.1115/IMECE2014-36006.

The study of joint contact mechanics to better understanding of all processes leading to cartilage degradation is very necessary. Elbow replacement will be the only option if both inner and outer components of the elbow have severe arthritis, or usually rheumatoid arthritis. It may also be recommended if there is osteoarthritis which makes the elbow stiff and painful, or a severe fracture of the elbow. Recently the operation known as Lateral resurfacing elbow replacement has been developed and introduced in hospitals. This operation has been designed for those people whose disease in the elbow involves mainly the outer compartment of the joint. The components are made from the metal and polyethylene and are fixed to the bones. An improper design of implants can lead to toxicity for patients caused by excessive amount of metal debris.

The purpose of this paper is to investigate the effect of roughness in Lateral resurfacing elbow implants. This paper develops a contact model to treat the interaction of the new surfaces fixed to the top of radius and humeral. The contact model describes the interaction of implant rough surfaces including both elastic and plastic deformations. In the model, surfaces are investigated as macroscopically conforming semi-spheres containing micron-scale roughness. The derived equations relate contact force on the implant and the minimum mean surface separation of the rough surfaces. Based on the distribution of asperity heights, the force is expressed using statistical integral function of asperity heights over the possible region of interaction of the roughness of the implant surfaces. Closed-form approximate equation relating contact force and minimum separation is used to obtain energy loss per cycle in a load-unload sequence applied to the implant.

Commentary by Dr. Valentin Fuster
2014;():V003T03A067. doi:10.1115/IMECE2014-36352.

Monte Carlo simulation of photon transport is formulated to solve transient radiative transfer equation through thin multilayered scattering-absorbing media with inhomogeneous properties. Though thin layers might seem to be geometrically insignificant, contribution of their radiative properties is relevant in predicting the behavior of most bioengineering, biomedical and space applications. Most traditional Monte Carlo models often fail to capture the presence of thin layers and account for its radiative properties. If the Monte Carlo model is implemented without unique features then the results of the simulation would show incorrect effect of thin layers since the path length of most photons would be significantly larger than the layer thickness and the evaluated photon travel path length would simply not feel the existence of the layer. Numerical and algorithmic features for computation of radiation transport through thin scattering and absorbing layers using the traditional Monte Carlo and an enhanced Monte Carlo model with features specifically developed for thin layers is presented and implemented for the analysis of backscattered radiation. It is observed that while Monte Carlo without special features defines the radiative effect of the layers, the refined technique indicates that layers have a great impact on the backscattered light, especially if the layer properties are distinctly different from those of the contiguous layers. The results have significant implications in the study of diagnostic applications of laser in biomedical applications since backscattered light is one of the non-invasive techniques available for detection of diseases and complements other known methods. Analyses of backscattered signals have also found use in the noninvasive methods of medical use especially in skin diagnostics.

Commentary by Dr. Valentin Fuster
2014;():V003T03A068. doi:10.1115/IMECE2014-36427.

Homogenization theory is utilized to study the effect on the axial stiffness of secondary osteons in cortical bone due to the presence of micro porous features (e.g., lacunae, canaliculi clusters, and Haversian canals). Specifically, 2 geometric characteristics were used to describe these features within the secondary osteons: volume fraction (% porosity) and shape (circular- or elliptical-shaped). Such information was determined for each individual porous feature from an image segmentation methodology developed earlier by Hage and Hamade. For each feature, aspect ratio vectors (or arrays of ratios for each individual porous feature) were used to classify each pore inhomogeneity as cylindrical, elliptical or irregular shape. Two prominent homogenization theories were used: the Mori-Tanaka (MT) and the generalized self-consistent method (GSCM). Using the results of image segmentation, it was possible to calculate the respective Eshelby tensors of each porous feature. To calculate the isotropic stiffness tensors for matrix (Cm) and pores (Cp) the Young’s modulus and Poisson’s ratio for the matrix (Em, νm) were assigned as obtained from literature and as those of blood (Ep=10MPa, νp= 0.3), respectively. The effective elastic stiffness tensors (C*) for the secondary osteons were obtained from which axial Young’s modulus was obtained as function of volume fraction (% porosity) of each pore type and their individual shapes. The normalized axial Young’s modulus was found to 1) significantly decrease with increasing volume fraction (%) of porosity and 2) for the same % porosity, to slightly decrease (increase) with increasing ratio of circular-shaped to elliptical-shaped (elliptical-shaped to circular-shaped) porous features. These findings were validated using experimental micro-indentation study performed on secondary osteons.

Topics: Bone
Commentary by Dr. Valentin Fuster
2014;():V003T03A069. doi:10.1115/IMECE2014-36645.

Dental restorative materials including amalgam, dental ceramic, gold alloy, dental resin, zirconia, and titanium alloy are used to reconstruct damaged teeth, as well as to recover their function. In this study, the mechanical properties of various dental restorative materials were determined using test specimens of identical shape and dimension under the same three-point bending test condition, and the test results were compared to enamel and dentin. The maximum bending force of enamel and dentin was 6.9 ± 2.1 N and 39.7 ± 8.3 N, and the maximum bending deflection was 0.12 ± 0.02 mm and 0.25 ± 0.03 mm, respectively. The maximum bending force of amalgam, dental ceramic, gold alloy, dental resin, zirconia, and titanium alloy were 1.9 ± 0.4 N, 2.7 ± 0.6 N, 66.9 ± 4.1 N, 2.7 ± 0.3 N, 19.0 ± 2.0 N, and 121.3 ± 6.8 N, respectively, and the maximum bending deflection was 0.20 ± 0.08 mm, 0.28 ± 0.07 mm, 2.53 ± 0.12 mm, 0.37 ± 0.05 mm, 0.39 ± 0.05 m, and 2.80 ± 0.08 mm, respectively. The dental restorative materials that possessed greater maximum bending force than that of enamel were gold alloy, zirconia, and titanium alloy. Gold alloy and titanium alloy had greater maximum bending force than dentin. The dental restorative materials that possessed greater maximum bending deflection than that of enamel were all of the dental restorative materials, and the dental restorative materials that possessed greater maximum bending deflection than that of dentin were all of the dental restorative materials except amalgam. The appropriate dental restorative materials for enamel are gold alloy and zirconia and for dentin is gold alloy concerning the maximum bending force and the maximum bending deflection. These results are expected to aid dentists in their choice of better clinical treatment and to contribute to the development of dental restorative materials that possess properties that are most similar to the mechanical properties of dental hard tissue.

Commentary by Dr. Valentin Fuster
2014;():V003T03A070. doi:10.1115/IMECE2014-37571.

The level of integration of digital microfluidics is continually increasing to include the system path from fluid manipulation and transport, on to reagent preparation, and finally reaction detection. Digital microfluidics therefore has the capability to encompass all steps of common biochemical protocols. Reported here is a set of analytical models for the design of a coplanar interdigitated multi-electrode array to be used as an impedimetric immunosensor in a digital microfluidic device for on-chip chemical reaction detection. The models are based on conformal mapping techniques, and are compared to results obtained from finite element analysis to discuss limitations of the model. The analytical models are feasible and inexpensive surrogates for numerical simulation methods.

Commentary by Dr. Valentin Fuster
2014;():V003T03A071. doi:10.1115/IMECE2014-38638.

The paper focuses on the effect of decalcification on microstructure and the mechanical and electrical properties of cortical bone. Decalcification is produced by placing the specimens into 5% vinegar acid for 72 hours. This acid treatment leads to a decrease in mass of the specimens 7.78 % (averaged over ten acid treated specimens). Microstructure of natural bone and acid treated bone is then compared using confocal microscopy. To estimate effect of acid treatment on electrical resistivity of bone, the specimens are rinsed and saturated with 0.9% NaCl solution for ten minutes. Then electrical resistance is measured by the four-point method and electrical resistivity is calculated. Averaging over ten acid treated specimens and ten control specimens show that decalcification lead to increase of electrical resistivity 5.85 times. Comparison of mechanical properties of natural and acid treated bones is done by three point bending using Instron 5882 testing machine. It is observed that 7.78 % mass loss in cortical bone yields reduction of the Young’s modulus about 2.7 times and bending strength of the specimens by 35%. A positive correlation between change in strength and Young’s modulus and electrical resistivity of the individual specimens is observed. The obtained results allows one to estimate changes in mechanical and electrical properties of bone from known losses in bone mass and, thus, non-destructively evaluate the decrease in bone strength through changes in electrical resistivity.

Commentary by Dr. Valentin Fuster
2014;():V003T03A072. doi:10.1115/IMECE2014-39804.

This work presents the fluid dynamic analysis of the mechanical prosthetic heart valves: Björk Shiley and Sorin Bicarbon™. Analysis of prosthetic valves is currently done with viscous fluids that emulate the behavior of blood; however the developed test bank, wind tunnel, uses air as the working fluid. This working fluid differs from those currently being used due to its low density and viscosity properties, which provides greater sensitivity to small changes in geometry and valve design variations. These features permit to identify relevant changes to the patient’s hemodynamic system based on the effect of the implanted valve.

Tests were performed by measuring the fluid-dynamics of both valves; the obtained results show accuracy with the valves’ performance under clinical conditions. The offset design of the Björk Shiley tilting disk gives the valve the ability to generate less blood trauma and increase laminar flow and the Sorin Bicarbon™ bileaflet has a larger orifice for better hemodynamic performance. Furthermore, the transversal pressure gradients and local effects such as turbulence and vortexes were also analyzed; and the obtained results are accurate according to the functionality, geometrical and structural characteristics of both valves at their real environment.

Commentary by Dr. Valentin Fuster

Biomedical and Biotechnology Engineering: Poster

2014;():V003T03A073. doi:10.1115/IMECE2014-39441.

Aquaponics is an eco-friendly system for food production utilizing aquaculture and hydroponics to cultivate fish and crop without soil. It is an inexpensive symbiotic cycle between the fish and plant. In an aquaponic system, fish waste (ammonia) is fed into the plant bed which acts as a bio-filter and takes the nitrate which is essential to grow vegetation. The fresh new water is then returned to the fish enclosure to restart the cycle. A unique advantage of an aquaponic system is conserving water more effectively compared to traditional irrigation systems. Conservation of water is accomplished by recirculating water between the plant bed and the fish habitat continuously. Organic fertilization of plants using dissolved fish waste is the other benefit of aquaponics. Utilizing plants as a natural alternative to other filters, requires less monitoring of water quality. In our project, an aquaponics system was designed and built in Lyle Center for Regenerative Studies at California State Polytechnic University of Pomona. The future purpose of our project is finding an optimized situation for the aquaponics system to produce food and save water more efficiently and eco-friendly.

Commentary by Dr. Valentin Fuster

Biomedical and Biotechnology Engineering: Transport Phenomena in Biomedical Applications

2014;():V003T03A074. doi:10.1115/IMECE2014-36428.

The influence of inflow conditions and human blood rheology on the wall shear stress distribution in a confined separated and reattached flow region is investigated. The governing mass and momentum conservation equations along with the Herschel-Bulkley rheological model are solved numerically using a finite-difference scheme. A parametric study is performed to reveal the influence of uniform and fully-developed inflow velocity profiles on the wall shear stress (WSS) characteristics using hemorheological models that account for the yield stress and shear-thinning non-Newtonian characteristics of human blood. The highest WSS or WSSmax, is always observed inside the flow separation region at a location corresponding to that of the corner vortex center. Uniform inflow results in higher WSSmax values in comparison with fully-developed inflow for moderate upstream flow restrictions. The opposite trend is observed for severe flow restrictions. Uniform inflow always results in smaller flow separation regions and WSSmax values at locations closer to the flow restriction plane. The yield shear-thinning hemorheological model always results in the highest observed peak WSS. The yield stress impact on WSS distribution is most pronounced in the case of severe restrictions to the flow.

Commentary by Dr. Valentin Fuster
2014;():V003T03A075. doi:10.1115/IMECE2014-38002.

This paper describes visualization of thrombus formation process on orifice flows and Couette flows by normal illumination. The aim is to investigate the effects of shear stress or shear rate on the thrombus formation or thrombus formation rate. It was found that (1) effect of flow types on the thrombus ratio was obtained and (2) quantitative evaluation of thrombus formation rate by our proposed CFD based prediction method was established for various flows.

Commentary by Dr. Valentin Fuster
2014;():V003T03A076. doi:10.1115/IMECE2014-38846.

Due to the increasing worldwide incidence of asthma, a growing usage of inhalation devices has been observed. Some of the pressurized Metered Dose Inhalers (pMDI) limitations have been overcome by the introduction of newly and improved Valved Holding Chambers (VHC), resulting in good patient acceptance.

The efficiency is assessed by the VHC Emitted Dose (ED), i.e. the amount of drug available to the patient.

Using the pMDI salbutamol sulfate formulation (Ventolin® HFA-134a) as the test drug, several VHC devices were assessed. These latest were grouped by material characteristics: dissipative (OptiChamber Diamond®, AeroChamber Plus®, Vortex®, A2A Spacer®), non-dissipative (SpaceChamber Plus®, Compact SpaceChamber Plus®, Volumatic®) and stainless steel (Nebuchamber®).

The pMDI + VHC were assembled to a filter housing, which comprises an induction port with similar USP Throat dimensions, and connected to a vacuum pump (calibrated at 15, 26 and 40 L/min). Using UV-Vis Spectrophotometry equipment at 244 nm, it was possible to determine its concentration for later mass calculation. For all the VHC devices tested, the total mass recovery percentage was between 85% and 120%.

At 26 L/min, the Vortex® VHC has shown the highest ED (47.3 ± 1.8 %).

The ED may not be dependent on the volume of the VHC. Although, further analysis of the results suggests the existence of a linear correlation between the ED and the VHC body length.

SpaceChamber Plus® results show an increase of the ED and, subsequently, a decrease in VHC deposition fraction, with the increase of airflow.

Commentary by Dr. Valentin Fuster
2014;():V003T03A077. doi:10.1115/IMECE2014-39438.

Ocular diseases cause vision deficiency and blindness in a substantial number of people in the world every day. Therefore, a controlled and sustained system of drug delivery to a specific spot within the eye is of interest for the ophthalmology community. The unique and complicated anatomy, physiology, and biochemistry of the eye make this organ highly resistant to drug delivery systems. The major challenge is to improve the efficiency of each treatment method along with avoiding the invasive techniques which damage the eye’s protective barrier tissues. In this work we make a computer model for the drug delivery to the anterior sections of the eye and provide a summary of transport characteristics of the eye, pharmacokinetics and efficacy of the utilized drugs. A two dimensional finite element model is utilized to solve the conservation of mass and momentum equations within different eye sub-domains such as cornea, anterior chamber, iris and sclera. The commercial software Comsol Multiphysics was utilized to obtain the profile of concentration in the eye and the grid independency of the numerical results has been checked. The results are being shown in terms of transient drug concentration profile in the eye subdomains. The influence of the modeling parameters on the efficiency of the drug delivery system is studied. The effect of physical variables such as drug molecular size and its bioavailability are investigated. The results are compared with the available literature data which are based on the drug diffusion within the domain.

Commentary by Dr. Valentin Fuster
2014;():V003T03A078. doi:10.1115/IMECE2014-40108.

Total liquid ventilation (TLV) is an emerging and promising mechanical ventilation method in which the lungs are filled with a breathable liquid. Perfluorocarbon (PFC) is the predominant liquid of choice due to its high O2 and CO2 solubility. In TLV, a dedicated liquid ventilator ensures gas exchange by renewing a tidal volume of PFC, which is temperature-controlled, oxygenated and free of CO2. A fundamental difference between TLV and conventional mechanical ventilation relates to the fact that PFCs are approximately 1500 times denser than air. This high density provides PFCs with a large heat capacity, turning the lungs into an efficient heat exchanger with circulating blood. The originality of this study is the development of a lumped thermal model of the body as a heat exchanger coupled to a liquid ventilator. The model was validated with an animal experimentation on a newborn lamb with the Inolivent-5.0 liquid ventilator prototype. TLV was initiated with a fast hypothermia induction, followed successively by a slow posthypothermic rewarming, a fast rewarming and finally a second fast hypothermia induction. Results demonstrate that the model was able to aptly predict, in every phase, the temperature of the lungs, the eardrum, the rectum as well as the various compartments of the liquid ventilator.

Topics: Ventilation
Commentary by Dr. Valentin Fuster

Biomedical and Biotechnology Engineering: Vibration and Acoustics in Biomedical Applications

2014;():V003T03A079. doi:10.1115/IMECE2014-36821.

Ceramic-on-Ceramic (CoC) bearings are an ideal choice for a total hip replacement because of the ceramic bearings’ longer wear life than Metal-on-Metal or Metal-on-Polyethylene bearings. Friction-induced squeaking has been reported in 1–10% of patients who have a ceramic-on-ceramic total hip replacement, which is a subject of annoyance. Many mechanisms have been proposed to address the squeaking phenomena in CoC hip replacements, but there is no consensus among researchers on the root cause behind the squeaking of hip implants. The goal of this study was to investigate the possible factors attributing to the hip squeak, and understand the underlying phenomenon based on the coupling stiffness of the bearing surface. Boundary conditions for the CoC hip bearing to produce audible noise were also identified. An explanted Stryker Trident CoC hip bearing that had been removed due to squeaking was analyzed visually and by computer simulation. Grey marks on the femoral head of the implant showed material transfer of titanium alloy onto the alumina head. Using modal analysis, the natural frequencies of all the components of the implant were determined. Random vibration analysis was conducted to identify the ideal boundary conditions for the CoC hip bearing.

The results from the modal analysis and calculated stiffness and damping coefficients were used in the mathematical two degree-of-freedom (DOF) model to calculate the velocity and position of the two masses in the system. State-Space plots of the parametric analysis were used to evaluate the stability of the system. Mathematical Analysis involved the investigation of the role of the frictional stick-slip phenomenon of the metal shell and ceramic liner on squeal. The size of the limit cycle provides an indication of the degree of severity of a noisy condition.

With only metallic shell affixed to the acetabulum constrained, the modal natural frequency was 3600 Hz which was very close to the free vibration results of the bearing. The Power Spectral Densities displayed the audible frequencies at 11.4 kHz. The limit cycle plots show that a variation in coupling contact stiffness has an influence on the behavior/stability of the system. The study underscored the relevance of material transfer on the bearing surface using the mathematical analysis by varying the coupling stiffness of the bearing surface. In addition, random vibration analysis in conjunction with the parametric analysis identified the ideal boundary condition to produce the squeal frequencies as observed by others.

Commentary by Dr. Valentin Fuster
2014;():V003T03A080. doi:10.1115/IMECE2014-37120.

An apparatus to provide a safer and more efficient non-invasive treatment of kidney stones is under development. The proposed non-invasive alternative is to produce a tightly focused high-intensity cavitation cloud right at the stone; the cloud being electronically steerable in real time to compensate for the respiratory movements which would significantly reduce the exposition of healthy tissues to damaging shock waves. The piloted cloud is produced by 19 independent novel shock wave generators that are geometrically oriented towards a single focal point. The real-time steering is accomplished by applying different emission delays between the shock wave generators. The steering capability of the 19-channel prototype was monitored in vitro using a pressure sensor and kidney stone analogs. Promising tests were also conducted on ex-vivo pigs to measure the erosion rate of implanted artificial kidney stones.

Topics: Cavitation , Kidney
Commentary by Dr. Valentin Fuster
2014;():V003T03A081. doi:10.1115/IMECE2014-37633.

The main driving mechanism during an asthmatic attack is the hyperconstriction of airway smooth muscle (ASM), which reduces the airway lumen and makes normal breathing difficult. The contraction can be relieved using bronchodilator drugs such as Isoproterenol, which induce temporary relaxation of the constricted airways. Pharmacological treatments are widely used in asthma, but their effectiveness varies from one subject to another, as do their side effects. Studies have shown that mechanical oscillations equivalent to physiological patterns such as breathing and deep inspiration in healthy airways can induce airway relaxation, but this type of response is not observed in asthmatics. Length oscillations seem to be a non-medicinal approach to treat ASM hyperconstriction present in many respiratory diseases such as asthma. Currently little is known about the effect of other oscillations’ patterns and their combination with breathing and deep inspiration on healthy and asthmatic airways during an asthmatic attack. Preliminary results obtained from in vitro and in vivo experiments in our laboratory indicate that the use of super imposed length oscillations (SILO) over normal breathing patterns can induce relaxation during an induced asthmatic attack on healthy and asthmatic subjects. These tests have been carried out using animal models which have been prepared under an acute protocol for the disease (new asthmatics), but these oscillations still remain to be tested in chronic asthmatic models (chronic asthmatics).

Topics: Oscillations
Commentary by Dr. Valentin Fuster
2014;():V003T03A082. doi:10.1115/IMECE2014-37731.

This paper describes the mechanism of cell proliferation promotion by mechanical vibration focusing on multilayering of cultured osteoblasts. After osteoblasts were cultured under the mechanical vibration of 0.5 G and 12.5 Hz, the saturated cell density reached approximately twice as high as control. In the vibration group, multilayer formation of osteoblasts was observed by fluorescent microscopy in contrast with almost single layer in the control group. Fluorescent staining demonstrated that the expression of N-cadherin, which plays an important role of cell-cell adhesion, was lower under mechanical vibration than control. Therefore, the application of mechanical vibration to osteoblasts can downregulate the expression of N-cadherin, resulting in weakening of cell-cell adhesion and multilayer formation followed by promotion of cell proliferation.

Commentary by Dr. Valentin Fuster
2014;():V003T03A083. doi:10.1115/IMECE2014-38107.

In order to establish a quantitative detection method for appearance in epileptic discharges (EDs), we propose using the model parameters in a Duffing oscillator, which is a nonlinear mathematical model. Extracting four frequency bands of delta, theta, alpha and beta waves from the time history of the electrocorticogram (ECoG) obtained from rats with induced EDs, we applied a sweep window to the time history for each band. So as to fit the equation for the Duffing oscillator to the time history of the ECoG, we used the least square method to determine the model parameters expressing characteristics of ECoG. The Duffing oscillator has three kinds of vibrational parameters and four kinds of parameters about the amplitude for the driving force with two predominant frequencies contained in ECoG. In order to examine the appearance time of the EDs and the change of ECoG characteristics, we determined the model parameters for each sweep window. When epilepsy occurs, we found that the amount of the parameters related to “conservation”, “dissipation” and “input quantities” increases. On the other hand, the parameter value corresponding to nonlinearity tends to decrease. It is found that the proposed method by the model parameters of the Duffing oscillator can be used in quantitative detection for EDs.

Commentary by Dr. Valentin Fuster
2014;():V003T03A084. doi:10.1115/IMECE2014-38844.

Intravascular super-harmonic imaging of microvessels is expected to assist understanding of atherosclerotic cardiovascular disease. A dual frequency intravascular (IVUS) ultrasound transducer is a core component transmitting at low frequency and receiving high order harmonics. A significant challenge in developing high performance dual frequency IVUS transducers is the isolation of the high frequency ultrasound echoes from the low frequency element while keeping the low frequency transmission pressure. An anti-matching layer with low impedance and quarter wavelength thickness was designed based on wave propagation theory. In both KLM modeling and prototype validation, the anti-matching layer successfully suppressed the aliasing echo to less than −20 dB. Transmission pressure of the prototype transducer was still high enough for microbubble nonlinear responses. High resolution (<0.2 mm) and high CTR (>12 dB) image was generated from super-harmonic imaging, which elucidated the capability of the transducer for intravascular microvessel detection.

Commentary by Dr. Valentin Fuster
2014;():V003T03A085. doi:10.1115/IMECE2014-38871.

Ultrasound imaging with high resolution and large field of depth has been increasingly adopted in medical diagnosis, surgery guidance and treatment assessment because of its relatively low cost, non-invasive and capability of real-time imaging. There is always a tradeoff between the resolution and depth of field in ultrasound imaging. Conventional ultrasound works at a particular frequency, with −6 dB fractional bandwidth of < 100%, limiting the resolution or field of depth in many ultrasound imaging cases.

In this paper, a bi-frequency co-linear array covering a frequency range of 5 MHz-20 MHz was investigated to meet the requirements of resolution and depth of field for a broad range of ultrasound imaging applications. As a demonstration, a 31-element bi-frequency co-linear array was designed and fabricated, followed by element characterization and real time sectorial scan (S-scan) phantom imaging using a Verasonics system.

Commentary by Dr. Valentin Fuster
2014;():V003T03A086. doi:10.1115/IMECE2014-39641.

This paper reports the experimental study on the enhanced cavitation yield via dual-frequency ultrasonic sonication and the multi-frequency single-bubble cavitation bubble modeling. The cavitation yield was characterized using the PCD (passive cavitation detection) method. A dual-frequency (1.5 MHz/3 MHz) pulse ultrasound was used in the tests. It was found that the sonication of dual-frequency ultrasound can produce a significant increase in cavitation yield compared with single-frequency irradiation. The possible mechanisms of the enhanced effect were explained by the single-bubble cavitation model, where the calculated radiated pressure generated by acoustic bubble cavitation was found greater in dual-frequency cases. The findings from this paper are promising for the design of multi-frequency ultrasound system with enhanced cavitation for a number of biomedical, biological and chemical processing applications.

Topics: Cavitation
Commentary by Dr. Valentin Fuster

Biomedical and Biotechnology Engineering: Viscoelasticity of Biological Tissues and Ultrasound Applications

2014;():V003T03A087. doi:10.1115/IMECE2014-37801.

Aging of soft tissues occurs through various mechanisms, which involve biochemical reactions, like glycation, oxidation and calcification of proteins in the extracellular matrix of the soft tissue. Aging leads to changes in the microstructure of the soft tissues which results in changes in its mechanical behavior. In this paper, a mixture theory based model that is thermodynamically consistent and applicable for chemically reacting systems is developed. The tissue (elastin) is modeled as a viscoelastic material. The model is simulated for uni-axial loading to study the effect of chemical reactions occurring in the tissue (elastin) on its mechanical response.

Commentary by Dr. Valentin Fuster
2014;():V003T03A088. doi:10.1115/IMECE2014-38261.

In this paper, spherical indentation testing is studied to evaluate the viscoelasticity of soft materials like human skin. Here, the Hertzian contact theory is functionally extended to evaluate indentations for the thin tissues. In the expansions, the technique used for evaluating the thickness of finite specimens is first explained by analyzing the experimental results of indentations. Then, the viscoelasticity of soft materials with finite thickness is theoretically derived by defining an equivalent indentation strain for the analysis of the indentation process. The expansions are examined to evaluate its reliability by applying them to measure the viscoelasticity of some soft materials. Furthermore, this technology is applied to the elasticity investigation of the human skin. Especially, the measurement results of viscoelastic characteristics of the skin of human face are shown as the first report. The influences of sex and ultraviolet rays and so on are discussed to reveal the mechanics of human skin in this report. Moreover, it is discussed about the validity of the device which measures the elasticity of the skin of human face.

Topics: Viscoelasticity , Skin
Commentary by Dr. Valentin Fuster
2014;():V003T03A089. doi:10.1115/IMECE2014-39256.

The purpose of this study is to disclose the mechanism about arterial behavior for the development of the in situ diagnosis of human artery. Then, a method which can evaluate the viscoelasticity of artery is proposed for this purpose. In this evaluation, three-element solid model is adopted as a constitutive model of arterial tissue. A cylindrical tube of silicone rubber which imitates human artery is used in the validation of the proposed method. Here, the specimen is inserted to an artificial system of circulatory organ. The material parameters of this model are identified from the pulsatile behavior of the tube cylinder. The evaluation method is validated to derive the parameters at the same time by using the applied pulsatile pressure and deformation and the method of least-square. In the validated results, it is shown that the method can evaluate in more detail about the mechanical evaluation of the pulsatile tube imitating artery.

Topics: Viscoelasticity
Commentary by Dr. Valentin Fuster

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