Imaging and Monitoring the Environment

2007;():1-2. doi:10.1115/BioMed2007-38036.

Low contrast imaging is of vital clinical importance and thus an important aspect of CT image quality. For example, soft plaque imaging, ground glass lung opacities, and soft tissue differentiation all depend upon excellent low contrast resolution. A primary factor in determining low contrast resolution is noise.

Commentary by Dr. Valentin Fuster
2007;():3-4. doi:10.1115/BioMed2007-38075.

Noninvasive blood flow characterization is essential to assess the health status of biological tissue and to evaluate the efficacy of therapies which target the microvasculature. Optimization of laser therapy for disfiguring vascular birthmarks is one specific clinical application. Current treatment protocols involve the use of high-power pulsed laser irradiation with parameters selected to induce selective photocoagulation of the targeted blood vessels. Protocol design is based largely on results from numerical modeling studies, which have predictive capability of the laser light distribution within the skin and subsequent photothermal response leading towards selective photocoagulation. However, the biological response of the microvasculature to therapeutic laser intervention remains a poorly-researched field. We hypothesize that the acute photothermal response of the microvasculature is a poor predictor of the chronic response, due to vascular remodeling processes which are not included in current modeling studies. To test this hypothesis, we employ an optical imaging method to assess blood flow dynamics in response to therapeutic intervention.

Commentary by Dr. Valentin Fuster
2007;():5-6. doi:10.1115/BioMed2007-38102.

Brain imaging requires high levels of precision and accuracy, especially for diagnostic or surgical applications. Histological sections represent the “gold standard” in high-resolution imaging. For high-fidelity volume renderings of stacks of histological sections image registration using linear and non-linear transformations is required. Non-invasive scanning techniques, such as MRI, CT, PET, etc., produce inherently lower resolution, but better aligned imagery. By combining invasive and non-invasive scanning techniques, the advantages of various modalities can be combined into a hybrid system which enables co-location of instantiated patient scans and high-resolution reference scans.

Commentary by Dr. Valentin Fuster

Simulation and Modeling

2007;():7-8. doi:10.1115/BioMed2007-38014.

A finite element model of the left atrium, incorporating detailed anatomical features and realistic material characteristics, was built to investigate the interaction of heart tissue and surgical instruments. This model was used to facilitate the design of an endoscopically deployable atrial retractor for use in minimally invasive, robotically assisted (MIRA) mitral valve repair. The left atrial geometry was imported directly from MRI data of an explanted porcine heart, and material properties were derived from experimental testing of cardiac tissues. Model accuracy was verified by comparing simulated cardiac wall deflections to those measured by MRI. Finite element analysis was shown to be an effective tool for analyzing instrument/tissue interactions and for designing surgical instruments.

Commentary by Dr. Valentin Fuster
2007;():9-10. doi:10.1115/BioMed2007-38019.

Photodynamic therapy (PDT) is currently being developed as a new therapeutic modality with minimal side effects in the treatment of many different types of cancers [1]. PDT requires three essential components, which includes a photosensitizing agent, activation light, and molecular oxygen [2, 3]. Light is one of the governing components for PDT, and the only component that can be controlled externally [4]. The understanding of light penetration in a tumor is critical for an efficient PDT protocol. A well-designed PDT protocol provides minimal microvascular damage and efficient killing of malignant tumor cells [5–7]. The depth of light penetration in a tumor depends on the microvascular nature of the tumor, amount of solid and liquid contents present, and the wavelength of the light source. The first two factors depend on the nature of the tumor tissue and therefore the optimal light dose is not standard for all tumors. Furthermore the liquid content of a tumor changes with the tumor temperature due to vasodilatation, and this in turn affects the depth of light penetration.

Commentary by Dr. Valentin Fuster
2007;():11-12. doi:10.1115/BioMed2007-38023.

This paper reports the design and simulation of Si-based ultrasonic nozzles (or atomizers) that consist of multiple Fourier horns at ultrasonic frequency ranging from 0.57 to 2.75 MHz. Such high frequency ultrasonic nozzles should produce monodispersed droplets (or drops) 2 to 6 μm in diameter, which are ideal to efficiently target medications to different locations within the respiratory system depending on the site of disease. 3-D simulations on vibration mode shape and impedance of the nozzles using a commercial finite element method (FEM) program, ANSYS, yield resonant frequencies of pure longitudinal vibration in good agreement with the measured values. The mode shape simulation also shows that at the resonant frequency the longitudinal vibration amplitude gain at the nozzle tip for 3-horn nozzle is 8, four times that for a single-horn nozzle.

Commentary by Dr. Valentin Fuster
2007;():13-14. doi:10.1115/BioMed2007-38027.

Delivery of drugs to the lungs as aerosols is regarded as an excellent route for local or systemic administration of drugs. Aerosols have been used traditionally for treating illnesses of the respiratory tract (e.g. asthma), but new perspectives and needs on inhalation therapy have recently emerged (e.g. insulin). The percentage of drug that reaches the targeted region, the so-called respirable fraction (RF), is in average only 30% of the dose provided to the patient. Thus, the development of more efficient formulations and devices remains an important issue.

Commentary by Dr. Valentin Fuster
2007;():15-16. doi:10.1115/BioMed2007-38073.

We sought to determine the effects of head rotation, lateral neck flexion, and traction force on brachial plexus (BP) nerve strain, specifically at C5-C6 (Erb’s point), and C7, C8, and T1 roots in a multi-“filament” 3D model of the fetal BP. Using our constructed simulator and a tailored data acquisition system, strain readings were recorded and accurate to within <2%. Using our model and a position-sensing system, controlled loads and deformations were applied to a fetal head attached to a flexible spine. For each simulation, we measured BP strain at Erb’s point, and C7, C8, and T1 roots. Increasing total traction force increases strain in the upper and middle nerves (Erb’s point, C7, and C8). Lateral neck flexion produces the most strain (up to 25.4±6.6% in Erb’s point with 4.5 kg (10 lbs) of traction), with concomitant head rotation magnifying strain levels by up to a factor of 1.7. Increasing head rotation and lateral neck flexion increases the strain in the lower nerve roots more than in the upper roots. in general, upper nerves undergo double the strain of lower nerves. Direct axial traction has the least effect, with 4.5 kg of traction producing a peak strain of 3.6±2.5% at Erb’s point. BP strain can be reduced at Erb’s point, C7, and C8 by maintaining neutral alignment between the head and trunk prior to applying traction, which should be minimized.

Commentary by Dr. Valentin Fuster
2007;():17-18. doi:10.1115/BioMed2007-38074.

In this work we focus on the fluid-structure interaction (FSI) problem of a St. Jude Regent 23mm bi-leaflet mechanical heart valve (BMHV) implanted in modeled straight aorta geometry with a simplified sinus. A FSI solver based on a recently developed curvilinear grid/immersed boundary method fluid flow solver is developed. The current numerical simulation focuses on the acceleration phase within the cardiac cycle when the leaflets are opening following the incoming flow. The simulated results are compared with experimental data with regard to the leaflet kinematics as well as valve induced wake vortical structures and excellent agreement between the simulation and measurements is reported.

Commentary by Dr. Valentin Fuster
2007;():19-20. doi:10.1115/BioMed2007-38082.

Spinal fusion surgery is one of the most common surgical procedures used to alleviate lower back pain. It is estimated that between 200,000 and 300,000 spine fusion procedures performed each year in the United States [1]. There has been an increase of approximately 8% per year in the frequency of lumbar fusions in the United States since 1980 [2]. Spinal fusion is indicated for treatment of degenerative disk disease, degenerative joint disease, scoliosis, and isthmic and degenerative spondlylotisthesis when more conservative treatments have failed to achieve relief.

Commentary by Dr. Valentin Fuster

Device Testing

2007;():21-22. doi:10.1115/BioMed2007-38046.

Hyperthermia, also called thermal therapy or thermotherapy, is a type of cancer treatment in which the aim is to maintain the surrounding healthy tissue at physiologically normal temperatures and expose the cancerous region to high temperatures between 43°C–45°C. Several methods of hyperthermia are currently under study, including local, regional, and whole-body hyperthermia. In local hyperthermia, Interstitial techniques are used to treat tumors deep within the body, such as brain tumors. heat is applied to the tumor, usually by probes or needles which are inserted into the tumor. The heat source is then inserted into the probe. Invasive interstitial heating technique offer a number of advantages over external heating approaches for localizing heat into small tumors at depth. e. g interstitial technique allows the tumor to be heated to higher temperatures than external techniques. This is why an innovative internal hyperthermia research is being conducted in the design of an implantable microheater [1]. To proceed with this research we need complete and accurate data of the strength, number and location of the micro heaters, which is the objective of this paper. The location, strength, and number of implantable micro heaters for a given tumor size is calculated by solving an Inverse Heat Transfer Problem (IHTP). First we model the direct problem by calculating the transient temperature field via Pennies bioheat transfer equation. A nonlinear least-square method, modified by addition of a regularization term, Levenberg Marquardt method is used to determine the inverse problem [2].

Topics: Heat transfer , Brain , Tumors
Commentary by Dr. Valentin Fuster
2007;():23-24. doi:10.1115/BioMed2007-38109.

Blindness due to degenerative retinal diseases such as Retinitis Pigmentosa (RP) and Age-Related Macular Degeneration (AMD) afflict millions of people worldwide. Recent advances in retinal implants that bypass damaged photoreceptor cells and electrically stimulate the remaining healthy retinal neurons show promise for restoring functional vision to the blind [1]. Current intraocular retinal prostheses driven by an external camera mounted on the subject’s head require slow and unnatural head movements. To allow for normal foveation and expanded depth of field, a novel intraocular camera (IOC) has been designed to work in conjunction with an epiretinal microstimulator array, as shown schematically in Fig. 1.

Topics: Prostheses
Commentary by Dr. Valentin Fuster

Bio-Sensors and Diagnostics

2007;():25-26. doi:10.1115/BioMed2007-38056.

Sudden cardiac death (SCD) accounts for over 325,000 deaths in the United States per year. Implantable cardioverter defibrillators (ICDs), about 100,000 of which are implanted each year, are used to diagnose and treat cardiac arrhythmias in patients that are at risk for sudden cardiac death due to ventricular fibrillation. Upon detection of an arrhythmia, the ICD has several treatment options, all of which deliver varied amounts of electric current to the myocardium. Detection of ventricular tachycardia (VT) or ventricular fibrillation (VF) prompts the ICD to administer high-energy defibrillation shocks, which can exceed 30J. The current method for sensing arrhythmias is the use of electrodes implanted in the myocardium which are capable of detecting electric potentials. The extensively studied algorithms that analyze electrogram sensor data have allowed ICD’s to achieve a 0% false negative rate for detection of fibrillation. The drawback, however, is the high false positive rate of over 22%. False positives result in inappropriate shocks which have detrimental effects on patient health and quality of life [1].

Commentary by Dr. Valentin Fuster
2007;():27-28. doi:10.1115/BioMed2007-38071.

The motions and loads experienced by the human spine are complex and have been the subject of much study over the years. The emerging field of intervertebral disc arthroplasty offers products that must function within this complex loading environment over long periods of time. So called “first generation” intervertebral disc designs accomplish this through one or more articulating surfaces. Second generation artificial discs attempt to mimic the multi-axial disc motion and stiffness exhibited by the natural human disc. The eDisc not only provides this type of viscoelastic motion, but also provides the first capability to sense loads and motions to improve patient outcomes.

Topics: Motion
Commentary by Dr. Valentin Fuster
2007;():29-30. doi:10.1115/BioMed2007-38089.

This paper describes a polymer-based cardiovascular shear stress sensor built on catheter for atherosis diagnosis. This flexible sensor detects small temperature perturbation as fluid past the sensing elements leading to changes in the resistance, from which shear stress is inferred. MicroElectroMechanical System (MEMS) surface manufacture technology is utilized for fabrication of the devices with biocompatible materials, such as parylene C, Titanium (Ti) and Platinum (Pt). The temperature coefficient of resistance (TCR) of the sensor is 0.11%/°C. When a catheter-based sensor is positioned near the wall of the rabbit aorta, our 3-D computational fluid dynamic model demonstrates that flow disturbance is negligible under steady state in a straight segment. The sensor has been packaged with a catheter and will be deployed into the aorta of NZW rabbits for realtime shear stress measurement.

Commentary by Dr. Valentin Fuster

Device Design and Development

2007;():31-32. doi:10.1115/BioMed2007-38025.

General non-invasive endovascular procedures for treatment of intracranial aneurysms involve stenting across the aneurysm neck, embolization and coiling of the aneurysm cavity. However it cannot be used to treat many wide-necked and fusiform intracranial aneurysms, or carotid-cavernous fistulae. Stent grafts will have the capability of completely preventing the blood flow into the aneurysm cavity or fistula rent, and thereby reducing the risk of aneurysm rupture in the brain. An endovascular approach of placing a stent graft would be a promising method [1–3].

Commentary by Dr. Valentin Fuster
2007;():33-35. doi:10.1115/BioMed2007-38062.

Failure of the cardiac or respiratory system is a common problem in the pediatric and neonatal intensive care unit. When conventional management fails to improve the child’s condition, extracorporeal life support such as extracorporeal membrane oxygenation (ECMO) can serve to provide life-saving temporary heart and lung support [1]. Renal failure often complicates care of these critically ill children on ECMO, leading to accumulation of fluid and volume overload that can worsen their heart and lung disease. Restrictive fluid management has been demonstrated to improve patient outcomes in acute lung injury.

Topics: Fluids , Membranes
Commentary by Dr. Valentin Fuster
2007;():37-38. doi:10.1115/BioMed2007-38067.

The efficacy of robotic systems in rehabilitation is well established. Many of these systems are fixed equipment that requires the user to visit a facility for treatment. Furthermore, current treatment options for pediatric patients with spastic dyplagia include manual stretching of the muscle groups and serial casting in conjunction with Botox injections. The goal of this work is to develop a dynamic orthotic to stretch the muscles of the lower calf. A subsystem of this project is the development of wearable sensor system to detect spasticity and control the system actuators. A system of thin film sensors embedded into a novel composite structure is proposed. In order to develop a dynamic orthotic to stretch the muscles of the lower calf, a subsystem of this project is the development of wearable sensor system embedded into a novel composite structure [1, 2, 3].

Topics: Design , Muscle
Commentary by Dr. Valentin Fuster
2007;():39-40. doi:10.1115/BioMed2007-38080.

Computed tomography (CT) guided percutaneous lung biopsies are conducted to retrieve samples of suspected cancerous tissue for diagnosis. This paper details the design and development of Robopsy™, an economical, patient-mounted, tele-robotic, radiolucent, needle guidance and insertion system which facilitates faster more accurate lesion targeting.

Topics: Lung , needles
Commentary by Dr. Valentin Fuster

Therapeutic Devices

2007;():41-45. doi:10.1115/BioMed2007-38034.

By all accounts cancer remains the leading cause of death for humans of age less than 85 years old. This is partly because of the fact that there has been success in addressing other competing diseases such as cardiovascular leading to an overall drop in the rate of such disease where as after four decades of research success in cancer therapy remains limited. This places a greater demand on developing new therapies to treat cancer. With recent advances in nanotechnology field as applied in medicine there are new opportunities to detect, more effectively target and treat cancer and monitor the therapy while minimizing the damage to normal tissues and cells.

Commentary by Dr. Valentin Fuster
2007;():47-48. doi:10.1115/BioMed2007-38044.

Drug Eluting Stent (DES) is a drug-device combination product. It is a metal stent coated with a pharmacological agent (drug). The drug interferes with the process of restenosis and prevents the reblocking of the artery. DES has been shown to reduce the incidence of restenosis from 20–30% range to single digits. A polymer is usually mixed -in with the drug to control the release of the drug into the vessel wall.

Topics: Drugs , stents
Commentary by Dr. Valentin Fuster

Next Generation Device Technology

2007;():49-50. doi:10.1115/BioMed2007-38052.

Theken Disc, LLC has developed an artificial spinal disc with an integrated microelectronics module to reduce post operative complications and speed return to work and function. During the first few months after implantation, it is very important to limit patient activity to prevent disc migration or dislodgement. The force monitoring capability provides realtime or stored data to assess patient’s ability to return to work. The microelectronics module monitors any dynamic high-load events that may take place, and immediately warns the patient of the high load by sending a wireless signal to a belt-worn audible alert unit.

Commentary by Dr. Valentin Fuster
2007;():51-52. doi:10.1115/BioMed2007-38088.

This paper describes the trial of making microcapsules including a bubble for shock wave drug delivery systems, evaluation of their mechanical properties and development of new driving mechanics of the microcapsules.

Commentary by Dr. Valentin Fuster
2007;():53-54. doi:10.1115/BioMed2007-38093.

An electronic microarray has been used to carry out directed self-assembly of higher order 3D structures from Biotin/Streptavidin and DNA derivatized nanoparticles. Structures with more than forty layers of alternating biotin and streptavidin and DNA nanoparticles were fabricated using a 400 site CMOS microarray system. In this process, reconfigurable electric fields produced by the microarray device have been used to rapidly transport, concentrate and accelerate the binding of 40 and 200 nanometer biotin, streptavidin, DNA and peroxidase derivatized nanoparticles to selected sites on the microarray. The nanoparticle layering process takes less than one minute per layer (10–20 seconds for addressing and binding nanoparticles, 40 seconds for washing). The nanoparticle addressing/binding process can be monitored by changes in fluorescence intensity as each nanoparticle layer is deposited. The final multilayered 3-D structures are about two microns in thickness and 50 microns in diameter. Work is now focused on assembling “micron size” biosensor devices from bio-molecule derivatized luminescent and fluorescent nanoparticles. The proposed structure for a nanolayered glucose sensor device includes a base layer of biotin/streptavidin nanoparticles, a layer of glucose oxidase derivatized nanoparticles, a layer of peroxidase derivatized nanoparticles, a layer of quantum dots, and a final layer of biotin/streptavidin nanoparticles. Such a device will serve as a prototype for a wide variety of applications which includes other biosensor devices, lab-on a-chip devices, in-vivo drug delivery systems and “micron size” dispersible bio/chem sensors for environmental, military and homeland security applications.

Commentary by Dr. Valentin Fuster

Student Posters

2007;():55-56. doi:10.1115/BioMed2007-38043.

The performance of prosthetic hands and robotic manipulators is severely limited by their having little or no tactile information compared to the human hand. Technologies such as MEMS, microfluidics, and nanoparticles have been used to produce arrays of force sensors, but these are generally not robust enough to mount on curved, deformable finger pads or to use in environments that include dust, fluids, sharp edges and wide temperature swings. Furthermore, it is not clear how the prosthetic controller will use the tactile information, so it is difficult to generate specifications for these sensors.

Commentary by Dr. Valentin Fuster
2007;():57-58. doi:10.1115/BioMed2007-38059.

Active steering at the distal tip can reduce stress on the flexible ureteroscope (FU) shaft by eliminating the internal angulation wires while also minimizing tissue trauma. A multi-segmented SMA wire actuator has been designed to produce smooth graded motion of the ultrathin scanning fiber endoscope (SFE). A steerable SFE distal tip (1-axis) is demonstrated using a three-step graded bending motion with a multi-tapped shape memory alloy (SMA) wire, power transistor switches, and binary parallel communication. The experimental bending radius and angle of the fabricated active tip (2-mm OD) is measured as 45-mm and 50°, respectively. Using nominal 4% strain of a 125-μm SMA wire, the experimental values are compared to the model predictions using a multi-link planar manipulator. A guidewire with eyes and active tip bending mechanism constitutes the new SFE, which is expected to reduce the procedural time and complications, eliminate X-ray guidance, and provide more space for adjunctive instrumentation, along with having better performance and possibly lower cost than FU.

Commentary by Dr. Valentin Fuster
2007;():59-60. doi:10.1115/BioMed2007-38060.

Upper extremity prostheses are a scarce necessity in less developed countries due to the lack of medical facilities, economic resources, and prevalent warfare. Prostheses have become a growing need as fifty-thousand amputations occur annually, with the current market being focused primarily on lower extremities. Leg prostheses have received much more attention and success than their upper extremity counterparts, due to their lower complexity that also yields lower cost. Prosthetic legs only need to fulfill basic motions such as walking and running, as opposed to the more complicated hands that encompass 22 degrees of motion. In less developed countries with few medical facilities, amputees need to travel long distances to find treatment. The objective is to design an affordable and easily assembled body-powered, below-elbow prosthetic device for adults that provides basic arm function and can be widely distributed in developing countries. Therefore, cost, availability, functionality, and simplicity are the primary considerations of the design.

Topics: Design , Prostheses
Commentary by Dr. Valentin Fuster
2007;():61-62. doi:10.1115/BioMed2007-38061.

It is called contracture that a joint’s range of motion is restricted. Range of motion exercise is effective to prevent contracture. However, if range of motion exercise by the physiotherapist is performed, a range of motion will improve, but if time not to exercise is long, contracture will decrease again. Then, a rehabilitation instrument for passive range-of-motion exercise which can use after exercise by the physiotherapist is required. A CPM for a knee is developed as such an instrument, and it is also used for an ankle. But, most of instrument used motors to get a high power. So, those are heavy and large size. Installation and movement of instruments at facilities are difficult, and it is also difficult to use freely at home.

Topics: Instrumentation
Commentary by Dr. Valentin Fuster
2007;():63-64. doi:10.1115/BioMed2007-38065.

For centuries, surgeons have heavily relied on scalpels and sutures to reshape cartilage. Reshaping the cartilaginous frameworks of the head and neck requires open surgery to counteract the intrinsic elastic forces that resist deformation. Recently, non-surgical techniques that use radio frequency or laser sources to reshape cartilage have been developed, but they rely on heat generation and may produce thermal injury [1,3]. We recently developed new techniques to reshape cartilage called Electro-Mechanical Reshaping (EMR ) that combines mechanical deformation with the application of low-level DC electric fields. Shape change is driven by electrochemical reactions that occur between electrodes placed in contact with the mechanically deformed specimen. Previous studies have shown that EMR of cartilage can be accomplished using graphite and aluminum surface electrodes [2,4]. In this study, EMR was further investigated with the use of needle electrodes that can be inserted into the mechanically deformed specimen rather than on the surface. Needle electrodes offer several advantages to surface electrodes because they can be incorporated into percutaneous surgical devices and instrumentation, deliver electric energy precisely to the site of desired shape change, and by design limit the spatial extent of tissue injury.

Commentary by Dr. Valentin Fuster
2007;():65-66. doi:10.1115/BioMed2007-38066.

Cell encapsulation in hydrogels or microcapsules is one of the approaches for providing a biomimetic microenvironment to support cell survival, proliferation and functions. Microcapsules in particular have been used to improve the mass transport properties and ease of delivery through injection. More importantly, the microenvironment in hydrogels or hydrogel microcapsules can be tailored by incorporation of relevant adhesion molecules and growth factors through chemical conjugation and physical encapsulation. These functionalized hydrogels have been shown to effectively influence cell adhesion, proliferation and differentiation. In this study, we describe the preparation and characterization of a novel hydrogel fiber by polyelectrolyte complexation. This unique fiber geometry can be useful for regeneration of cylindrical tissues and for coculture of two different cell types inside and outside the fiber membrane.

Commentary by Dr. Valentin Fuster
2007;():67-68. doi:10.1115/BioMed2007-38076.

Biosensors are analytical devices to detect biological reactions. Fluorescence labeling is the most widely used method. Labeling free methods are desired in some cases because it can save the time and effort of the labeling step and provide real-time observation for the reactions.

Commentary by Dr. Valentin Fuster
2007;():69-70. doi:10.1115/BioMed2007-38104.

The aim of this project is to develop a cost effective point of care (POC) microfluidic diagnostic device to detect the presence of active tuberculosis (TB) in Human Immunodeficiency Virus (HIV) co-infected individuals in developing countries. According to the World Health Organization (WHO), 8.8 million people develop new cases of active TB each year in addition to the many millions of untreated existing cases. Current TB diagnostic tests are less accurate in detecting active TB in HIV co-infected individuals. Hence, the development of a fast, affordable, portable and handheld device to accurately detect active TB is necessary. As there are different stages of TB infection, it is important to detect the presence and progress of the infection. Our device design utilizes a serological assay in a microfluidic device, incorporating protein antigen microarrays spotted onto nitrocellulose, to detect TB at various stages of the disease. Features of the design include a microfilter to separate serum from the blood sample to be used, a passive pump to ensure uniform continuous flow, and an immunosensor to detect and analyze results.

Commentary by Dr. Valentin Fuster
2007;():71-72. doi:10.1115/BioMed2007-38105.

Accounting for more than 13 million deaths a year, infectious diseases have become the world’s biggest killer of children and young adults worldwide [1]. Diagnostic tools and technologies are vital towards identifying the presence and treatment of these diseases. Detection methods have commonly relied on DNA using polymerase-chain-reaction (PCR), however antibody methods have become popular due to growing trends in technology and detection sensitivity. ImmPORT Therapeutics, a leading group in generating infectious disease proteome microarrays, has developed multiplex systems for comprehensive analysis of immune responses to multiple infectious diseases [2]. Current microarray handling however requires conventional lab-bench methods that require whole-day processes and large amounts of user-handling confined to laboratory settings. Miniaturization of laboratory processes would provide numerous advantages in terms of cost, time, portability and multistage automation in addition to what is already offered. The proposed microfluidic device is a colorimetric enzyme-linked-immunosorbant assay (ELISA) for antibody detection of infectious agents that draws on ImmPORT Therapeutics technology with a purpose of decreasing reagent volumes and times potentially unattainable through conventional methods.

Commentary by Dr. Valentin Fuster
2007;():73-74. doi:10.1115/BioMed2007-38110.

The balloon-type pneumatic actuator [1] has been proposed, the development of this actuator is advancing as the miniaturization is easy and the driving efficiency is high compared with past pneumatic actuators.

Commentary by Dr. Valentin Fuster


2007;():75-80. doi:10.1115/BioMed2007-38006.

This study provides procedural tools that can be used in concert with a computer algorithm to simulate the two-phase flow development of a higher density, tracer fluid inside a vertical tube. The problem arises in the context of a tracer fluid (e.g., a contrast agent) being injected into a neutral fluid such as blood. Based on cell fractions of tracer fluid obtained numerically, absorbency profiles are extrapolated. These are shown to compare favorably with laboratory x-ray samples realized under similar flow conditions. At low Reynolds numbers, one finds that a downward profile exhibits a more elongated frontal boundary than predicted by laminar flow theory of a single-phase, Newtonian fluid. The observed stretching of the denser fluid is confirmed experimentally and can be attributed to the combined effects of gravity assistance near the core and viscous resistance near the wall. In gravity-resisted flow, a reverse behavior is observed. A blunter frontal boundary is established during upward motion. In both cases, the role of gravity is weakened with successive increases in the Reynolds number. This behavior suggests the existence of a Reynolds number above which gravitational bias can be neglected in any flow orientation. It is hoped that this study will set the pace for a broader investigation of two-phase motion characterization of a tracer fluid under various flow conditions and orientations.

Commentary by Dr. Valentin Fuster
2007;():81-82. doi:10.1115/BioMed2007-38009.

Studies of reliability in current practice indicate that reliability based on conventional methods requires a nonlinear transformation to a set of normal distributions, which effectively changes the shape of limit state function. In this paper, the general formulation of safety for aluminum elements and the associated methods of analysis are reviewed. Direct simulation is used to find the probability of failure. It is concluded that direct simulations of safety of aluminum elements of Pr (probability of failure) by failure counting is a good method to achieve acceptable safety factors.

Commentary by Dr. Valentin Fuster
2007;():83-87. doi:10.1115/BioMed2007-38011.

In the recent years, the focus of ever-progressing scientific and technological advancements is continuously drifting towards the rehabilitation engineering. The development in the field of “mobility aid” has led to research, which has transformed conventional manual attendant-style wheelchairs to electric-powered wheelchairs with improved control through joysticks, sensors and micro-controllers. Consumers with limited mobility (pain in legs, permanent injury etc.) and elderly users, who cannot independently operate a powered wheelchair due to their hands impairment, have to rely upon third-party assistance during transfers to secure their wheelchair. Most ‘Mobility Assistance Equipment’ manufacturers for the orthopaedically handicapped individuals have not been able to adequately address such problems. With mobility being a key factor in all aspects of human life, this project proposes a design to allow hands impaired people, who cannot walk to orient themselves in, and navigate through, complex environments with the help of foot controlled wheel chair. This paper presents design and development of a battery-powered wheelchair that will be operated by foot controls, based upon the need assessments of such consumers. The Electronic System is a basic speed control circuit designed and provides for four motion configurations — reverse, stop, slow, and fast.

Topics: Design
Commentary by Dr. Valentin Fuster
2007;():89-90. doi:10.1115/BioMed2007-38012.

Shape memory and superelastic capabilities coupled with good biocompatibility give Nitinol the ability to provide functionality seldom possible with traditional engineering alloys. In this study the effect of heat treatments of 300 ∼ 550°C for 2 ∼ 180 minutes on Ti-50.8%Ni (at.%) wire of 30% and 50% cold work was investigated. Transformational and mechanical properties were characterized through the bend and free recovery (BFR) method and tensile testing. Thermally activated precipitation and annealing processes occurred. Annealing processes tended to increase the slope and the total strain recovery of the BFR plots. Two TTT diagrams were constructed illustrating the trends in the Austenite Finish Temperature (Af ) of the wires. A maximum precipitation rate occurred at approximately 450°C. Precipitation strengthening was evident in both 30% and 50% cold-worked wires. However, only in the former did an increase in UTS occur. Recrystallization began at approximately 450°C for both wires.

Commentary by Dr. Valentin Fuster
2007;():91-96. doi:10.1115/BioMed2007-38015.

Hole serves various purposes in any machine element. These holes may be round, square, rectangular or any other shape depending on the requirement. For round holes, the machines are available in the market. But for square or any other type of holes, the Methods presently used are broaching, electrode-discharge machine (E.D.M.), electro-chemical machine. These are very expensive and require special tools or machines.

Commentary by Dr. Valentin Fuster
2007;():97-98. doi:10.1115/BioMed2007-38030.

The number of people who are suffering from Functional gastrointestinal disorders is increasing. There are, however, rare diagnostic methods for the functional gastrointestinal disorders because functional disorders show no evidence of organic and physical causes [1, 2]. Recently our research group identified that the gastrointestinal tract well in the patients with the functional gastrointestinal disorders is more rigid than healthy people. we noticed it with palpating the abdominal regions overlaying the gastrointestinal tract. Therefore we developed a system to detect the rigid organs with ultrasonic technique, which can quantify the characteristic above related to the rigidity of the gastrointestinal tract well.

Commentary by Dr. Valentin Fuster
2007;():99-102. doi:10.1115/BioMed2007-38035.

Miniaturization of devices is driving replacement of electronic components with surface mount technology (SMT) equivalent parts, including any embedded sensing devices. In many cases the size of the sensor is restricted by the minimum size of the package rather than by the die. Other solutions to preserve real-estate involve manual mounting of the die onto substrates that have gone through an SMT assembly process. The +/-2g accelerometer presented here is, to our knowledge, the first wafer-level packaged device with solderable terminals that allows the silicon die to be mounted directly onto a substrate in a standard SMT process and without the need for stressisolating interposers. With its small footprint and ceiling requirements (2.1 × 2.9 × 0.8 mm3 ), and robustness and high performance it is the smallest commercially-available packaged accelerometer suitable for medical applications where these characteristics are critical. The device features terminals that are electrically and mechanically separated but robust enough to withstand large shear forces that may occur during use and board assembly. The device was solder mounted on a variety of substrates without affecting its performance. Most significantly, both device and solder joints were able to withstand extended thermal cycling over a wide temperature range (-55 to 125°C). In this paper, we present the device design, the performance and the long-term reliability test results of this novel and high-performance device on a variety of substrates and solder materials.

Commentary by Dr. Valentin Fuster
2007;():103-104. doi:10.1115/BioMed2007-38038.

The use of the SEM to make direct surface measurements on small test specimens enables the FEA analyst to construct and validate an individual specimen model. The technique is also valuable to engineers so that they can calibrate their fatigue test samples before and after fatigue test regimes.

Commentary by Dr. Valentin Fuster
2007;():105-106. doi:10.1115/BioMed2007-38040.

Most of the recent studies for image uniformity assessment involve signal to noise ratio (SNR) analysis computed over various combinations of mean grey level and variance [1–2] to quantify the speckle contrast and hence the depth of penetration (DOP). Speckle is auto correlated in time but not in space. Electronic noise always present at the bottom of the image, instead, is uncorrelated both in time and space. The extension of the area in which only the speckle is visible, gives an estimate of the penetration depth. The correlation coefficient of two subsequently acquired frames can be computed to quantify image uniformity where depth at which the correlation coefficient falls below a fixed threshold is defined as penetration depth.

Commentary by Dr. Valentin Fuster
2007;():107-108. doi:10.1115/BioMed2007-38041.

The study of the rehabilitation of the upper arm is an important issue in the Rehabilitation field due to: (i) the rapid growth of the older population [1, 2] and (ii) traumatic brain injury [3]. More specifically, the increase of the elderly at 2.4% per year and the increase in the probability of a stroke with age; in fact, this pathology is the first cause of invalidity in Europe where it occurs at a rate 60% higher than in the US. Moreover, it is necessary to take into account other degenerative pathologies, such as Parkinson’s. MIT-MANUS is the robotic system developed at the MIT Lab to rehabilitate the upper limb by means of exercises which guide or perturb the spontaneous movement of the brain-injured subject [4]. Its disadvantages are: (i) the loss of reality, because the patient reaches a visual target with the robot handle, which does not correspond to a 3D movement, and, especially, (ii) the high cost. The study of reaching is divided in two branches: reaching towards a still or a moving target. In the first case, it is preferable to explore the working space [5] to investigate the possible residual movements [6] and to recuperate the functions of the shoulder joint. Instead, as regards the moving target, there has been much research done because significant performance improvements were obtained in pathological patients [7]. So, the use of a ball projection machine is proposed [8]; it has the advantage to allow 3D trajectories but many disadvantages: (i) control only on initial impulse; (ii) not-reproducibility of trajectory; and (iii) risk in using with non-collaborative subjects. Instead, a system with magnetic coupling to move the object in 2D is proposed [7]; it allows the production of many trajectories and the control of dynamic parameters. The coordination between elbow and shoulder joints has been studied in the unconstrained reaching towards a still target [9].

Topics: Robotics
Commentary by Dr. Valentin Fuster
2007;():109-110. doi:10.1115/BioMed2007-38042.

A Monte Carlo model with special features for modeling of radiation transport through very thin layers has been presented. Over the decades traditional Monte Carlo model has been used to model highly scattering thin layers in skin and may inaccurately capture the effect of thin layers since their interfaces are not perfectly planar and thicknesses non-uniform. If the Monte Carlo model is implemented without special features then the results of the simulation would show no effect of the outer thin layer since the path length of most photons would be significantly larger than the layer thickness and the resulting predicted photon travel would simply not notice the presence of the layer. Examples of multi-layered media are considered where the effect of a very thin absorbing layers is systematically examined using both the traditional Monte Carlo and that with new features incorporated. The results have profound implications in the diagnostic and therapeutic applications of laser in biomedicine and surgery.

Topics: Simulation , Modeling
Commentary by Dr. Valentin Fuster
2007;():111-112. doi:10.1115/BioMed2007-38047.

Development of an implantable wireless heating system capable of controlling the growth of malignant brain tumors is proposed by heating the tumor to hyperthermic temperatures (43–45°C) for a specified period of time. This investigation involves designing and fabricating microheaters to heat up the tumor and developing a complete system by integrating various components like pulse generator, microheaters, and wireless power transfer system. A software tool will aid the physician in the treatment planning. The software take the geometry and size of the tumor as input and provide strength and location of heaters as output. Depending on these outputs the physician can then decide the location of heaters in the tumor and the thermal dosage required to treat the patient. A minor surgery is required for implanting the system where the heaters are placed stereotactically into the brain tumor through holes made in the skull by small catheters slid. The number of required heaters depend on the tumor size. Minimal invasiveness, wireless power transfer and a scientific method to determine the location and strength of the heat sources are some of the significance of this study.

Topics: Tumors , Heating
Commentary by Dr. Valentin Fuster
2007;():113-114. doi:10.1115/BioMed2007-38048.

Gastrointestinal (GI) disease affects millions of people worldwide and costs billions of dollars annually. Because the symptoms of GI diseases are often vague, physicians are often presented with gastrointestinal disease in advanced stages. Because conventional endoscopes often cannot reach all the way through the 20-foot small bowel, exploratory surgery previously was necessary to enable physicians to complete their diagnosis.

Commentary by Dr. Valentin Fuster
2007;():115-116. doi:10.1115/BioMed2007-38050.

Pedicle screws are commonly used in spine surgery to implant and affix metal devices to the spine. These screws are most commonly associated with cases that require rod or plate implantation. Use of pedicle screws in osteoporotic patients, however, is limited because they suffer from low bone mass density (BMD). The low BMD is harmful to patients in two ways — it leads to increased incidence of spinal trauma and also prevents surgeons from instrumenting osteoporotic patients because screws do not achieve the required fixation in osteoporotic patients [1]. The risk of trauma is increased due to the brittle bone and vertebral compression fractures, resulting in spinal misalignment and increased risk of future trauma. Instrumenting these cases with rods or plates, however, is impossible because osteoporotic bone is not strong enough to “hold” pedicle screws in, i.e., prevent screws from pulling out [2, 3].

Commentary by Dr. Valentin Fuster
2007;():117-118. doi:10.1115/BioMed2007-38051.

In microfluidic related chemical and biological applications, mixing on the micro scale is important and has been considered as one of the most challenging tasks. With a trend for polymeric microfluidic systems, a simple yet efficient passive micromixer is highly preferred [1–4]. We developed a novel passive micromixer with 3D porous microstructure on a polymer chip. The fabrication process uses high-intensity focused ultrasound to selectively foam gas-impregnated polymers. The selective ultrasonic foaming technique is simple, low-cost, and biocompatible. The porous microstructure is easily controlled by adjusting the parameters of the ultrasonic foaming process. The 3D porous microstructure can split, stretch, fold and break the mixing flows in microfluidic channels and thus dramatically improve the mixing efficiency.

Commentary by Dr. Valentin Fuster
2007;():119-120. doi:10.1115/BioMed2007-38054.

Controlled and targeted drug delivery systems have gained a lot of interest as they offer numerous benefits such as precise dosing, reduced side-effects and increased patient compliance. We have designed a microelectromechanical systems (MEMS) drug delivery device that is capable of releasing drugs in a controlled and programmable manner. This self-powered device does not require any external stimulation or control to achieve pulsatile release of drugs. The device consists of multiple reservoirs containing the drug embedded together with a water-swellable polymer. The swelling of the polymer upon contact with water and the resulting pressure generated is used as an actuation mechanism to release drugs from each reservoir. The programmable release of the drug from the device is achieved by controlling the diffusion rate of water from the surrounding environment into each reservoir. The drug is released from the reservoir when the swellable polymer absorbs water from the environment and generates enough pressure to break an overlying rupturable membrane. We have demonstrated that controlled and pulsatile drug delivery can be achieved using this delivery device, without any external power or control.

Commentary by Dr. Valentin Fuster
2007;():121-122. doi:10.1115/BioMed2007-38063.

It is expected that by the years 2025 ours will becomes a super-aged society because people’s lifetimes will be extend by advances in medical treatment, and consequentry the number of the disabled and elderly people with the sicknesses and disabilities will increases. Therefore, the development of devices that promote an independent lifestyle for disabled and elderly people is the disired achievement. Herein, our aims is to develope an operable support device for the arm in which the artificial muscle actuator and gas spring assists in producing power according to the degree of an individuals muscle power.

Topics: Actuators , Muscle , Springs
Commentary by Dr. Valentin Fuster
2007;():123-124. doi:10.1115/BioMed2007-38064.

A modified Mach-Zender set-up in reflection is applied to record and reconstruct holographic amplitude and phase images. A charged couple device (CCD) is used to record a hologram and numerical reconstruction algorithms are then applied to rebuild the hologram for obtaining both phase and amplitude information. One could also focus on multiple focal planes from a single hologram, similar to the focusing control of a conventional microscope. The morphology and behavior of mammalian cells is determined by an interaction between signals from the intracellular matrix and the cellular responses. It is important to note that the physical aspect of the extracellular matrix is as significant as the chemical nature of it. Specifically the stresses, mechanical forces, and the profile of the external environment have major effects on cell behavior. The mechanical and physical characteristics of a tissue are greatly dependent on a hierarchical spatial arrangement of its extra-cellular matrix components. A key player in the ECM is collagen which exhibits significant tensile strength on the cellular scale. Digital holographic microscopy (DHM) is applied to study the deformation of collage matrix in response to cell migration.

Commentary by Dr. Valentin Fuster
2007;():125-126. doi:10.1115/BioMed2007-38068.

We describe the design and testing of an implantable miniature infusion pump that uses a rechargeable battery as a power source. This design includes a receiver printed coil that allows inductive power transfer from a transmitter coil wound around a 20 cm diameter charging unit and a frequency-gated optical sensor that allows activation of the pump at a distance using pulses of infrared light. This mini pump can be charged in the home cage by inductive power transfer, and then operates independently from its power link in freely moving animals.

Commentary by Dr. Valentin Fuster
2007;():127-128. doi:10.1115/BioMed2007-38069.

Microfluidic droplet systems have shown great promise and numerous advantages in the recent development of high throughput chemical and biochemical assays. With precise metering and manipulation of reagents at small scale, various applications such as protein crystallization [1], nanoparticle synthesis [2], physiological fluids diagnostics [3] and etc. have employed such systems and achieved success.

Commentary by Dr. Valentin Fuster
2007;():129-130. doi:10.1115/BioMed2007-38070.

Lab-on-a-Chip technology now becomes increasingly attractive due to advantages such as reduced sample size, reduced reagent consumption, shortened analysis time, potential for high throughput and automation and reduced costs, leading to the potential for manufacturing of disposable devices. On such microchip system, the ability to handling microfluid is important. Extensive microfluidic handling componets including microflow regulator, microfluidic sensor, microvalve and micropump have been reported. Although these microfluid handling methods are successful, for the polymer based microfluidic device, a simple design, easy fabrication and the ability to integrate into the microsystem lacks report. In this paper, we presented such microvalve by utilizing the hydrophobicity of the PDMS material, a popular biocompatible material widely used in microfluidic system. The valve utilized air trapped on the side wall of microchannel by a special microconcave structure design. Controlled by an external coil heater, the trapped air will be enlarged to reduce channel width and so reduce the fluid flow in the microchannel. The valve can work in on/off mode or on flow regulating mode depending on specific flow control requirement.

Topics: Microfluidics , Valves
Commentary by Dr. Valentin Fuster
2007;():131-132. doi:10.1115/BioMed2007-38072.

Environmental conditions can have major influence on the lifetimes and reliability of active implantable medical devices (e.g., neurostimulators, cochlear implants, internal cardioverter defibrillators). These environmental conditions can range from those encountered by the device in processing and production to transportation and storage to actual operation. Although one might argue that the environmental conditions found in the first two situations are harsher than those of the third, failures that result from those situations are screened before implantation. If we assume that the active medical device is in perfect operational form at the time it is implanted, it will still experience a host of environmental conditions that can affect reliability. In fact, the ultimate goal of these medical devices is to restore the patient, wherever they may reside, to normal activities. A list of some environmental conditions that may be experienced by a device implanted in a representative patient is found in Table 1.

Topics: Reliability
Commentary by Dr. Valentin Fuster
2007;():133-134. doi:10.1115/BioMed2007-38077.

Our society depends on communication, the most natural form of which is speech. Trauma, disease and the normal aging process will cause many to suffer degraded or lost vocal fold function, and it has been observed that this number is growing [1]. The vocal folds are the vibrating structures in the larynx that enable us to generate voice, from speech to opera singing. The vibrating portions of the folds consist of an external 0.1mm thick layer of epithelial cells, a soft, gel-like 0.5mm thick layer called the lamina propria (LP), a 0.3mm thick vocal ligament and an underlying thyroarytenoid muscle [2]. The fundamental frequency of speech in men is in the 100–150Hz range, and between 200 and 300Hz in women [3].

Commentary by Dr. Valentin Fuster
2007;():135-136. doi:10.1115/BioMed2007-38078.

The process of osseointegration is the firm anchoring of a surgical implant by the growth of bone around it without fibrous tissue formation at the interface. This process is critical for long-term implant success. The ability to monitor this process in vivo would allow for personalization of loading protocols to increase the rate of implant success overall by ensuring that implants are not over or under loaded during recovery. Accordingly, there is a strong need for an instrument that has the sensitivity to noninvasively measure osseointegration in vivo. One of the objectives of the present study was to assess the performance of an instrumented percussion probe for quantitatively monitoring the osseointegration process.

Commentary by Dr. Valentin Fuster
2007;():137-138. doi:10.1115/BioMed2007-38083.

It has been well supported in the literature that using compression screws is the preferred method to achieve fixation of an arthrodesis [1, 2]. Indications for isolated subtalar arthrodesis include trauma, arthritis, talocalcaneal coalition, adult acquired flatfoot, posterior tibial tendon dysfunction, and Charcot neuroarthropathy [3, 4]. With the increase in bone screw shapes and designs, there is a desire to achieve the best compression generated by a type of screw so as to promote excellent bone healing and outcome for the patient; this will also allow the stability of the construct achieved by the screw and its placement to be determined. As indicated by Wheeler, et. al. [5] screw choice, compression, stability and loading can be very important when it comes to healing of fractures in small bones.

Topics: Screws , Compression
Commentary by Dr. Valentin Fuster
2007;():139-140. doi:10.1115/BioMed2007-38084.

Back pain is one of the most widespread sources of chronic pain in the human population. The etiology of back pain is nearly as diverse as the treatment measures used to alleviate the discomfort. However, when conservative options have been exhausted, without achieving adequate relief, the patient and physician often turn to surgical options to eliminate the source of pain.

Topics: Bone , Surgery
Commentary by Dr. Valentin Fuster
2007;():141-142. doi:10.1115/BioMed2007-38086.

The success of a spinal fusion is often judged by the amount of relative motion between vertebrae following surgery. Proper fusion is aided by fixation instrumentation as well as bone growth subsequent to surgery. In order to allow for proper fusion it is necessary for instrumentation to properly fix the vertebrae until sufficient bone growth has occurred. In many cases pedicle screws are used to provide posterior support. It is the purpose of posterior instrumentation to increase the rate of fusion [1]. However, due to deterioration in the holding capacity of the posterior instrumentation; the quality of the fixed joint can begin to degrade. If this deterioration is significant enough it requires removal or revision of the fixation instrumentation.

Commentary by Dr. Valentin Fuster
2007;():143-144. doi:10.1115/BioMed2007-38087.

As motion preservation implants begin to replace fusion devices for lumbar degenerative disc disease, preclinical mechanical testing of these devices is critical to predicting their in vivo safety and efficacy. ISO and ASTM standards committees have tried for years to develop a universal test standard for all lumbar disc implants. The eDisc, an elastomeric/titanium disc replacement, is substantially different in its mechanical performance than the Synthes ProDisc or J&J Charite disc. These discs rely on ball and socket motion about a fixed or moving center or rotation to provide motion restoration in 3 to 5 axes. In contrast, the eDisc has viscoelastic motion in 3 translation and 3 rotational directions, just as in the natural human disc.

Commentary by Dr. Valentin Fuster
2007;():145-146. doi:10.1115/BioMed2007-38091.

This paper describes the effects of gradient of cytokine concentration on chemotaxis of neutrophile by observing the motion in liquid with adding cytokine concentration. The aim of this investigation is to distinguish the driving force by Marangoni effects from amebic motion.

Commentary by Dr. Valentin Fuster
2007;():147-148. doi:10.1115/BioMed2007-38092.

In this paper, a new temperature-controllable heat-acupuncture system is developed to replace the conventional heat-stimulating therapy practiced with moxibustion and heat acupuncture. The improved heat-stimulating characteristics of the developed system are experimentally verified.

Topics: Heat , Temperature
Commentary by Dr. Valentin Fuster
2007;():149-150. doi:10.1115/BioMed2007-38094.

The objective of this research is to design and optimize a mini/micro-channel based concentrator of E. coli and integrate it with an acoustic wave biosensor. A computational research has been carried out using the state of the art computational software, CFD-ACE with water as bacteria bearing fluid. E. coli bacteria have been modeled as random discrete particles tracked by solving the Lagrangian equations. The design challenges are to achieve high particle to water ratio, high enough Reynolds number to avoid bacteria swimming, and various particle boundary conditions. The optimized design has achieved concentration of about an order of magnitude higher than the inlet concentration at a flow velocity much higher than the bacteria swimming speed under various particle-boundary interactions. Bypass channels have been used to separate concentrated water-particle mixture and to put this mixture directly onto the biosensor’s bacteria detecting surface for safe and precise installation of the biosensor in the fluidic chip.

Commentary by Dr. Valentin Fuster
2007;():151-152. doi:10.1115/BioMed2007-38095.

This research aims at developing a new device for normalization of a hyperactive gag reflex response. The gag reflex protects the airway against the entrance of unwanted material. Individuals with a hyperactive gag reflex response exhibit either a forceful motor response which may include vomiting or trigger the gag reflex in the anterior 2/3 of the oral cavity or non-oral body parts (3).

Topics: Engines , Cavities
Commentary by Dr. Valentin Fuster
2007;():153-154. doi:10.1115/BioMed2007-38100.

The objective of this research is to study the effects of surface roughness on flows through nano/micro channels with a focus on designing better biomedical devices. A two dimensional computational model for fluid flow based on Lattice Boltzmann (LB) method has been applied first to a 10 μm width channel with flat boundary conditions and the flow profiles have been found to have an excellent comparison with analytical results. Rough boundary conditions using rectangular tooth-shaped corrugations giving about 0.25 μm average roughness have then been applied to the same 10 μm channel flow. We have observed significant differences in the velocity profiles between the flows with rough and flat boundary conditions. Boundary slips have also been observed in case of flows with rough boundary conditions. Surface roughness effects have increased or the differences between the flows with rough and flat boundary conditions have increased with decreased channel widths.

Commentary by Dr. Valentin Fuster
2007;():155-156. doi:10.1115/BioMed2007-38103.

An optical fiber biosensor has been presented for monitoring drug delivery inside the body in real time. Over the decades several optical techniques have been realized to monitor drug delivery, however, those are not that much efficient as the one presented here. In this paper, a new micromachined optical fiber biosensor has been demonstrated with both theoretical and numerical models. The detailed fabrication processes have been outlined in a multimode optical fiber which is based on MEMS fabrication. The sensor is designed by following the basic principle of Fabry-Perot interferometer. The optical biosensor presented here could be able to detect and monitor the drug delivery in real time and it could also potentially be used in the area of microfluidics, nano research and other biomedical applications.

Commentary by Dr. Valentin Fuster
2007;():157-158. doi:10.1115/BioMed2007-38114.

This paper describes a method for determining a digital representation of a remote sensing element using a novel and lower power method of analog to digital conversion [1]. This conversion process is most effective for low-frequency and very low current Radio Frequency Identification (RFID) sensing systems where the sensing element tags are powered by an inductively coupled carrier signal of fixed frequency. This method eliminates the need for a traditional, large and power-hungry Analog-to-Digital Converter (ADC). This approach is being developed for an orthopedic application that measures the invivo strain on titanium rods to help surgeons better understand the progress of fusion in spinal fusion surgery [2]. Previous work has been shown using the difference of two clocks for sending digital data from the reader to the tag [3], whereas this approach is optimized for sending digital data in the other direction, from tag to the reader. The sensor element may be a resistive or capacitive device integrated into an oscillator of variable frequency. This variable oscillation signal is then divided down and used as the time base to a frequency counter clocked by the recovered carrier signal. In recovering and using the carrier signal as an internal clock, an additional on chip oscillator is not necessary. The resultant value then undergoes additional post processing to add a unique identification string, a CRC check word, Manchester encoding, and Frequency-Shift Key (FSK) encoding for load modulation transmission [3,4].

Commentary by Dr. Valentin Fuster

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