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ASME Conference Presenter Attendance Policy and Archival Proceedings

2017;():V010T00A001. doi:10.1115/IMECE2017-NS10.
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This online compilation of papers from the ASME 2017 International Mechanical Engineering Congress and Exposition (IMECE2017) 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presenter attendance policy, if a paper is not presented at the Conference by an author of the paper, the paper will not be published in the official archival Proceedings, which are registered with the Library of Congress and are submitted for abstracting and indexing. The paper also will not be published in The ASME Digital Collection and may not be cited as a published paper.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

Micro- and Nano-Systems Engineering and Packaging: Applications of Micro and Nano Systems in Medicine and Biology

2017;():V010T13A001. doi:10.1115/IMECE2017-70975.

This paper presents the use of a piezoelectric resonator, which can be applied to investigate live cells activity in water-based toxic solution. We perform toxicity tests using commercial quartz crystal microbalance (QCM). The QCM used in this research has the resonant frequency of 10 MHz and consists in an AT-cut crystal with gold electrodes on both sides. This QCM was transformed into a functional biosensor by integrating with polydimethylsiloxane (PDMS) culturing chambers. Rainbow trout gill epithelial cells (RTgill-W1) were cultured on the resonators as sensorial layer. The fluctuation of the resonant frequency, due to the change of cell morphology and adhesion, is an indicator of water toxicity. The shift of resonant frequency will provide information about the cells viability after exposure to toxicants. Experiment setup, fabrication process, and sensor sensitivity testing are addressed. The toxicity result shows distinct responses for different ammonia concentrations.

Commentary by Dr. Valentin Fuster
2017;():V010T13A002. doi:10.1115/IMECE2017-71771.

This paper presents a theoretical analysis of using a distributed-deflection sensor with a built-in probe for mechanical measurement of soft tissues with curved surface. The core of the sensor is a rectangular polydimethylsiloxane (PDMS) microstructure with a built-in probe on its top and an electrolyte-enabled resistive transducer array at its bottom. Upon being pressed against a tissue region, the built-in probe assists in avoiding extrusions and generating deformations necessary to conform to the curved surface of the tissue region. Consequently, the true mechanical properties of the tissue translate to the spatially distributed deflection in the microstructure, which registers as resistance changes by the transducer array. A simplified 1D theoretical model is created and utilized for correlating the design parameters of the sensor and the probe to the tissue parameters, in order to meet three performance criteria for the tissue-probe-sensor interaction in measurement. Costal cartilage tissues are chosen as the tissue example for analysis. The analyzed results provide the design guideline for the numerical analysis in the future for accurate determination of the design parameters for soft tissues of interest.

Commentary by Dr. Valentin Fuster
2017;():V010T13A003. doi:10.1115/IMECE2017-72209.

Manipulation of fluids in a small volume is often a challenge in the field of Microfluidics. While many research groups have addressed this issue with robust methodologies, manipulation of fluids remains a scope of study due to the ever-changing technology (Processing Tools) and increase in the demand for “Lab-On-a-Chip” devices. This research peruses the flow pattern and fluid mixing behavior in a metallic circular electrode, charged with AC voltage.

In this study, micromixing in a circular electrode pattern device is demonstrated with numerical and experimental values. Experiments were performed using two buffer solutions with conductivities 1.62 S/m and 0.0732 S/m. The efficiency of mixing was found to be three to five times faster than the normal diffusion process. It was found that the increase in the conductivity of fluid increases the efficiency of mixing in the proposed device.

Commentary by Dr. Valentin Fuster

Micro- and Nano-Systems Engineering and Packaging: Applied Mechanics and Materials in Micro- and Nano-Systems

2017;():V010T13A004. doi:10.1115/IMECE2017-70039.

As a step in employing the strained silicon in enhancing a MEMS piezoresistive based 3D stress sensor performance, this paper studies the influence of pre-stretching silicon atoms on the temperature coefficient of resistance (TCR). Extracting accurately the TCR is very influential for the piezoresistive based stress sensor. For this purpose, a piezoresistive sensing rosette was fabricated on strained and unstrained silicon substrates. The pre-strained state was integrated during microfabrication using an intrinsic stress produced by highly compressive plasma enhanced chemical vapor deposition (PECVD) silicon nitride layer, which induces global biaxial tensile pre-strain onto the substrate. Under a stress free thermal loading, the TCR for both strained and unstrained chips were calibrated using an environmental chamber. Comparing the calibration results in both strained and unstrained silicon, the tensile pre-strained silicon has larger TCR than that in unstrained silicon. Moreover, over the surface concentration range used in this work, the strained silicon shows the same unstrained silicon trend, which is, the TCR is increased proportionally with the surface concentration.

Topics: Temperature , Silicon
Commentary by Dr. Valentin Fuster
2017;():V010T13A005. doi:10.1115/IMECE2017-70589.

Covetic aluminum has been researched for its mechanical properties. It has been credited with higher strength in tensile and fatigue loading [1,2]. Modest changes in temperature during tensile testing of covetic aluminum causes significant changes in the ductility and tensile strength. Increasing the temperature from 15 °C to 44 °C causes a decrease in the tensile strength down to 63.8% but an increase in the ductility up to 117% [3]. To further study the environmental effects, microtensile testing was carried out in an environmentally-controlled chamber using a hybrid microtester at high and low relative humidity. MEMS-scale dog-bone shaped specimens with a cross section of 200 × 250 microns were machined from bulk covetic aluminum using a CNC for milling their contours and a ram-type EDM for detaching them from the work piece. The chamber was purged with gases low or high in moisture maintaining a positive pressure. An Omega sensor-controller unit was used to regulate the temperature and relative humidity of the chamber. The results of the tests show a reduction of ductility at high relative humidity. The implications of the results are discussed in relation to the reliability of MEMS structures.

Commentary by Dr. Valentin Fuster
2017;():V010T13A006. doi:10.1115/IMECE2017-71002.

Throughout the course of one day, the human body goes through numerous mechanical activities. These activities, while usually not very powerful individually, produce an ample amount of energy collectively. This mechanical energy can be harvested into electrical energy via piezoelectricity. Recent research into piezoelectric nanocomposites has yielded techniques to foam the materials into softer, porous structures more suitable for human comfort. This study focuses on using a host polymer polydimethylsiloxane (PDMS) and citric acid to create foams. Citric acid, a common industrial chemical blowing agent (CBA), is used in this project due to its capabilities to produce foams with consistent pore sizes and distribution. These foams, coupled with piezoelectric nanoparticles, are fabricated, analyze, and tested. They are mechanically characterized using tensile testing. Electrical characterization is carried out using an integrated mechanical-electrical testing setup. These foams are lighter, softer, and can produce higher electrical output than non-porous counterparts. We believe that these foams have great potential in upcoming piezoelectric technology.

Commentary by Dr. Valentin Fuster
2017;():V010T13A007. doi:10.1115/IMECE2017-71228.

Water injected foamed asphalt application in warm mix asphalt (WMA) accounts for more than 90% of all WMA technologies in past several years in the United States (US). Among different asphalt foaming variables: foaming temperatures, foaming water content (FWC), and air pressure are the major controlling factors of foamed asphalt binder characteristics. Foaming induced binder volume expansion and durability of the expanded volume are two contributing factors of foamed asphalt binder properties and foamed mixtures workability. This study evaluates the effect of FWC on foamed asphalt binder properties through a non-contact method. A laser distance meter has been utilized to record the foaming induced binder volume expansion and subsequent foamed bubbles collapse rate. Recently developed four foaming parameters such as expansion ratio (ER), half-life (HL), foaming index (FI), and stability of semis-table foamed binder bubbles (k-values) have been evaluated to characterize foamed asphalt binder. It is seen that addition of higher FWC results in a higher expansion and durability of overall foamed bubbles. Foaming parameter analysis also shows that semi-stable foamed bubbles durability is fairly constant in higher FWCs. Foamed binder rheology is also found to be correlated with FWCs.

Commentary by Dr. Valentin Fuster
2017;():V010T13A008. doi:10.1115/IMECE2017-71762.

Asphalt concrete (AC) consists of asphalt binder and aggregate. Aggregate consists of: coarse aggregate and fines. Asphalt binder creates a coating or film around the aggregate, which is defined as the binder phase of AC. Fines are believed to be trapped inside an asphalt film or mixed with asphalt binder, creating a composite material called mastic. Thus, AC has three phases: mastic, asphalt film binder, and coarse aggregate. All these phases play major roles in performance of AC. Researchers have performed various tests on asphalt binder at micro scale to understand the macro scale behavior of AC. However, test methods developed and performed on binders, to this day, are mostly rheological shear and bending beam tests. No studies have been conducted on the compression stiffness or modulus and hardness of and binder, rather than shear and binders stiffness. In addition, the existing tests used in the asphalt area cannot be performed on binder and mastic while they are an integral part of AC. Nanoindentation tests can be performed on aggregate and asphalt binder while they are integral parts of AC. Because, in nanoindentation test, a nanometer size tip, which is smaller than binder film thickness as well as other phases. In the study, Performance Grade (PG) 64–28 was used for the study, same binder had been used afterwards to characterize asphalt and AC. A loading rate of 0.005 mN/sec, a dwell time of 200 sec and a maximum load 0.055 mN were employed in the study. In the current study 20 indentations were done on the asphalt binder sample and 100 indentations were done on AC sample, due to heterogeneity of the sample. However, to identify a specific phase in AC sample, the current study adopts the depth range technique for as same loading protocol. The depth rage of binder phase was acquired by independent indentation on same asphalt binder sample. As, asphalt is known to be a viscoelastic material that exhibits creep behavior, the creep compliance of asphalt binder was used for validation of the depth range assumption. The validation of phase identification was done by comparing the asphalt binder phase creep response while they are integral part of AC with creep response of independent asphalt binder sample under nanoindenter. The comparison shows depth resolution technique can successfully identify the binder phase of AC.

Commentary by Dr. Valentin Fuster
2017;():V010T13A009. doi:10.1115/IMECE2017-71813.

Asphalt concrete’s dynamic modulus (|E*|) is one of the key input parameters for structural design of flexible pavement according to the Mechanistic Empirical Pavement Design Guide (MEPDG). Till this day, pavement industry uses |E*| to predict pavement performance whether the material is hot mix asphalt (HMA) or warm mx asphalt or Reclaimed Asphalt Pavement (RAP) mixed HMA. However, it is necessary to investigate the correlation of |E*| with laboratory performance testing. In this study, laboratory dynamic modulus test was conducted on four different asphalt concrete mixtures collected from different construction sites in the state of New Mexico and mastercurves were obtained to evaluate dynamic modulus (|E*|) for a wide range of frequency. In addition, fatigue performance of these mixtures was predicted from the mastercurves and compared with the laboratory fatigue performance testing. Fatigue performance of these mixtures was evaluated from the four point beam fatigue test. The laboratory results show a good agreement with the predicted value from mastercurves. It is also observed from this study that the fatigue life of the asphalt concrete materials decreases with increase in |E*| value.

Commentary by Dr. Valentin Fuster
2017;():V010T13A010. doi:10.1115/IMECE2017-71840.

Fracture toughness and fracture energy release rate are two important parameters to understand the crack propagation within any material. Fracture toughness of asphalt concrete (AC) is vital to explain the fatigue cracking and low temperature cracking of asphalt pavement. These two types of distresses are still unsolved issues for asphalt researchers. Measuring fracture toughness of AC is not a new phenomenon. Recently, researchers have used several techniques to measure the fracture toughness of AC. Tests like semi-circular bending (SCB) and disk-shaped compact specimen (DCT) testing have been used to measure the fracture toughness of the AC. From the SCB or DCT tests, past researchers have shown that crack in AC propagates through mainly binder and mastic phase. All these conventional tests are carried out in macro scale. It is important to understand that before propagation of these macro scale cracks, the cracks initiates at the nano/micro scale level. With the increment of the loads these nanoscale cracks become macro scale cracks and propagates through the sample. Therefore, it is important to understand the cracks at nanoscale. In this study, nanoindentation test was introduced to measure the fracture toughness of the asphalt concrete. In a nanoindentation test, the sample surface is indented with a loaded indenter. For this test, Berkovich indenter with load control method was used. A field cored asphalt concrete sample was used for this study. The sample was collected by coring at interstate 40 (I-40) near Albuquerque, New Mexico. The sample was field aged for four years. The maximum load applied in this study was 5-mn and the unloading was done at a faster rate than the loading rate. From the load-displacement curves of the nanoindentation tests, fracture toughness of the samples was measured. The unloading curve of the nanoindentation test was further used to obtain reduced modulus of the asphalt concrete using Oliver-Pharr method. In this study, fracture energy is thought of as a portion of irreversible energy. This irreversible energy is comprised of plastic energy and energy required for propagation of crack. By analyzing the load displacement curve along with the maximum indentation depth, energy release rate and mode I fracture toughness of asphalt concrete was measured.

Commentary by Dr. Valentin Fuster
2017;():V010T13A011. doi:10.1115/IMECE2017-72419.

Soccer is played all over the world in a wide range of temperature environments. One of the objectives of this numerical study is to determine whether temperature has an effect on the body and performance of a soccer ball. Another object is to aerodynamically determine the effect of stitching pattern of the ball on its flight.

The soccer ball was modeled in ANSYS Workbench and tested with thermal-stress analysis tool at nominal temperatures of 0°C, 20°C, and 40°C. The maximum deformation of a soccer ball at normal condition occurred at 40°C which was 1.0503 cm as compared to the 0.9587 cm at 0°C. This normal condition means when the ball is subjected to an internal pressure of 80 kPa which is the standard inflation pressure. When an external 2700 Pa pressure was applied to the soccer ball which is the average force of a kick, the maximum deformation again occurred at 40°C which was 5.2289 cm as compared to the 4.7599 cm at 0°C. Therefore, the stiffness of the ball materials decreased as the temperature increased. This reveals that the ball delivers a greater force at the surface of contact when the temperature drops.

The second part of this study as mentioned earlier was to study the aerodynamic effect on a soccer ball traveling through the air at a certain speed. Two types of soccer ball were analyzed for this reason to see which of the two flew better in the air. The two types were a regular FIFA soccer ball with stitching and a normal soccer ball without stitching. Two tests were performed on both types of the soccer ball. These tests were done using ANSYS FLUENT and the sought out output parameters were velocity, pressure, Reynolds Number and drag force. In the first test the soccer balls were rotating in the air and in the second test the soccer balls were not rotating in the air. For the first test, the ball without stitching had the higher velocity, Reynolds Number, and drag force, which were 126.2 m/s, 2.420 × 106, and 122.6 N respectively. This means the ball without stitching is experiencing a more random turbulent flow and is being pulled more into the direction of the drag force. This happens because the soccer ball without stitching will rotate faster and won’t have stitching patterns to create friction that will slow down the flow. For the second test, the ball with stitching had the higher velocity, Reynolds Number and drag force which were 42.22 m/s, 8.095 × 105, and 16.81 N respectively. This means the soccer ball with stitching is experiencing a random turbulent flow and is being pulled in the direction of the drag force because the stitching patterns are not in complete contact with the air to create friction.

Commentary by Dr. Valentin Fuster
2017;():V010T13A012. doi:10.1115/IMECE2017-72471.

Photostriction is best defined as the generation of strain in a material via light irradiation. In essence the photostrictive effect is a result of the combination of the photovoltaic and converse-piezoelectric effects. When light comes into contact with the surface of a photostrictive material, the photovoltaic effect causes the generation of a large amount of voltage. The converse-piezoelectric effect in turn converts the produced voltage into mechanical motion, which induces strain in the material. Photostrictive ceramics are considered excellent materials for use in advanced actuation technologies. This is due to their ability to be activated through irradiation of light, which provides advantages over conventional actuators, which include remote control capability, freedom from physical actuation, and reduced electromagnetic (EM) interference. Conversely conventional actuators require hard wired connections to transmit control signals that can produce EM interference, creating signal noise. Photostrictive ceramics have also found use in the manufacturing of micro electromechanical systems, also known as MEMS technology, mostly due to their wireless capabilities.

Photostrictive materials are ferroelectric ceramics that exhibit the photostrictive effect. PLZT, (Pb, La)(Zr, Ti) O3 ceramics doped with WO3, exhibit large photostriction deflection under uniform illumination of light, and have potential uses in numerous micro-electro-mechanical systems as a result of this property. The objective of this research is to numerically investigate the effect of light intensity on transverse deflection of an overhanging beam model, and to assess the effect actuator size has on deflection for a propped cantilever beam model using finite element analysis technique. The current research results is then compared with the validated results of other studies on PLZT using other model types.

From this numerical investigation it has been observed that for an overhanging beam model, the transverse deflection of PLZT actuators has a direct relationship to the intensity of the light applied in order to induce photostriction. It has also been observed that this relationship applies over a large range of light intensity upwards of 4000 mW/cm2, boosting maximum deflection into the micron range (1E−6 – 1E−7 m). With regard to the propped cantilever beam model, it has been observed that incomplete PLZT coverage of the cantilever beam portion of the model caused upwards transverse deflection. However, as the amount of PLZT actuator was increased, the deflection behavior exponentially approached negative values. By comparing these results with similar studies on alternate model types, it was confirmed that for beams deposited with PLZT actuator, light intensity and actuator size and surface coverage will affect the transverse deflection of the beam in the same manner regardless of the beam model.

Commentary by Dr. Valentin Fuster

Micro- and Nano-Systems Engineering and Packaging: Computational Studies on MEMS and Nanostructures

2017;():V010T13A013. doi:10.1115/IMECE2017-70318.

A nano-scale strip of graphene is known as graphene nano-ribbon (GNR). Previous studies have shown that the armchair-type GNR (aGNR) can open the electronic band gap at room temperature, and the band gap increases monotonically with the decrease in the width of aGNR. The critical width at which aGNR shows semi-conductive characteristics at room temperature is about 70 nm, when it is passivated by hydrogen on both sides. However, the electronic band structure varies frequently as a function of the number of carbon atoms along its width direction. In order to decrease the large variation of the band gap of aGNR to control the electronic properties of GNR for highly sensitive sensors and high performance devices, the electronic band structure of various dumbbell-shape structure of aGNR was analyzed by first-principles calculations based on the density functional theory using implemented in SIESTA package. It was shown that the width of aGNR had a large effect on the electronic band structure and the amplitude of the fluctuation of the band gap as a function of the number of carbon atoms decreased drastically. The electronic band structure of various GNRs under the application of uniaxial strain was also analyzed by using the first-principles calculations, in this study. It was confirmed that the effective band gap of aGNR thinner than 70 nm varies drastically under the application of uniaxial strain, and this result clearly indicates the possibility of a highly sensitive strain sensor using dumbbell-shape GNR structures.

Commentary by Dr. Valentin Fuster
2017;():V010T13A014. doi:10.1115/IMECE2017-71070.

In this paper, the dynamic performance of two parallel micro-cantilever beams is investigated and the results are presented. The dynamic response is of high interest in MEMS structures as it is related to the performance of the micro-devices. The micro-cantilever beams can be easily fabricated and yield high sensitivity to variations of physical quantities. In this work, the dynamic response of two parallel flexible cantilever beams subjected to a difference of potential is analyzed. This configuration was modeled as mass-damper spring systems with two degrees of freedom. Such a system can be used to measure the viscosity of liquids. This viscosity is related to damping between two masses representing the two beams in the discrete system model. The fabrication of two identical beams using MEMS fabrication processes may be difficult as the fabrication process may yield some variabilities. Thus, the two beams may be slightly different which will be reflected in their mass and stiffness. This condition was assumed in the proposed model. As the system is sensitive to the applied difference of potential such that the pull-in voltage represents a good indicator of the sensitivity performance. The dynamic analysis was carried out at potentials close to the pull-in value. Stability of the system was evaluated and the responses of the beams were calculated at a potential close to the pull-in voltage. The sensitivity of the system was calculated for different viscosities of liquid between two beams. It was found that an increase of the viscosity yields higher nonlinearity and consequently loose of accuracy while assuming linear stiffness for the beams. In this research, the stiffness of micro-cantilever beams was calculated from small deflection theory of beams. However, there are other methods that could be considered to evaluate the stiffness of the beams. One of this different methods was considered and the sensitivity of the modeled stiffness is discussed. Since the stiff nonlinear differential equations cannot be solved analytically, the numerical approach was exploited. In this work ISODE method from Maple software was used to solve the model described by the two differential equations.

Commentary by Dr. Valentin Fuster

Micro- and Nano-Systems Engineering and Packaging: Design and Fabrication, Analysis, Processes, and Technology for Micro and Nano Devices and Systems

2017;():V010T13A015. doi:10.1115/IMECE2017-70323.

In three-dimensional packaging module which have been used in electronic equipment, the size of partial interconnections and total structure have been continuously miniaturized for improving the performance of the products. Due to the fluctuation of the mechanical properties of the component materials and the drop impact towards the fragile modules during manufacturing and operation, the final residual stress varies easily in a chip of the 3-D structure. Both the static and dynamic changes of the stress distribution induce the variation of the performance of electronic devices and the degradation of their long-term reliability. It is, therefore, important to control and optimize the residual stress quantitatively. In this study, a stress sensor which can monitor the change of the local residual stress in 3-D module was developed by applying the piezoresistance effect of single-crystalline silicon. The sensor was embedded in a silicon chip, and it can measure the periodic stress in a silicon chip assembled by area-arrayed bump structure. The impact stress during the manufacturing process was successfully monitored by using this sensor. It was also confirmed that the effective amplitude of the impact stress varies drastically depending on the mechanical properties of the stacked thin films.

Commentary by Dr. Valentin Fuster
2017;():V010T13A016. doi:10.1115/IMECE2017-70485.

The sensitivity and linearity trade-off problem has become the hotly important issues in designing the piezoresistive pressure sensors. To solve these trade-off problems, this paper presents the design, optimization, fabrication, and experiment of a novel piezoresistive pressure sensor for micro pressure measurement based on a combined cross beam - membrane and peninsula (CBMP) structure diaphragm. Through using finite element method (FEM), the proposed sensor performances as well as comparisons with other sensor structures are simulated and analyzed. Compared with the cross beam-membrane (CBM) structure, the sensitivity of CBMP structure sensor is increased about 38.7 % and nonlinearity error is reduced nearly 8%. In comparison with the peninsula structure, the maximum non-linearity error of CBMP sensor is decreased about 40% and the maximum deflection is extremely reduced 73%. Besides, the proposed sensor fabrication is performed on the n-type single crystal silicon wafer. The experimental results of the fabricated sensor with CBMP membrane has a high sensitivity of 23.4 mV/kPa and a low non-linearity of −0.53% FSS in the pressure range 0–10 kPa at the room temperature. According to the excellent performance, the sensor can be applied to measure micro-pressure lower than 10 kPa.

Commentary by Dr. Valentin Fuster
2017;():V010T13A017. doi:10.1115/IMECE2017-71656.

Three-dimensional (3D) printing is a novel technology whose versatility allows it to be implemented in a multitude of applications. Common fabrication techniques implemented to create microfluidic devices, such as photolithography, wet etching, etc., can often times be time consuming, costly, and make it difficult to integrate external components. 3D printing provides a quick and low-cost technique that can be used to fabricate microfluidic devices in a range of intricate geometries. External components, such as nanoporous membranes, can additionally be easily integrated with minimal impact to the component. Here in, low-cost 3D printing has been implemented to create a microfluidic device to enhance understanding of flow through carbon nanotube (CNT) arrays manufactured for gene transfection applications. CNTs are an essential component of nanofluidic research due to their unique mechanical and physical properties. CNT arrays allow for parallel processing however, they are difficult to construct and highly prone to fracture. As a means of aiding in the nanotube arrays’ resilience to fracture and facilitating its integration into fluidic systems, a 3D printed microfluidic device has been constructed around these arrays. Doing so greatly enhances the robustness of the system and additionally allows for the nanotube array to be implemented for a variety of purposes. To broaden their range of application, the devices were designed to allow for multiple isolated inlet flows to the arrays. Utilizing this multiple inlet design permits distinct fluids to enter the array disjointedly. These 3D printed devices were in turn implemented to visualize flow through nanotube arrays. The focus of this report though, is on the design and fabrication of the 3D printed devices. SEM imaging of the completed device shows that the nanotube array remains intact after the printing process and the nanotubes, even those within close proximity to the printing material, remain unobstructed. Printing on top of the nanotube arrays displayed effective adhesion to the surface thus preventing leakage at these interfaces.

Commentary by Dr. Valentin Fuster
2017;():V010T13A018. doi:10.1115/IMECE2017-71674.

This work demonstrates the manufacturing process of micro- and nanofluidic devices consisting of independent, aligned carbon pipes with potential applications as micro- and nanoscale dispensing systems, electrodes, and tools with which to study fundamental micro- and nanofluidics. A low-cost, high-throughput chemical vapor deposition (CVD) process was utilized to deposit carbon within novel silica-based templates. This simple template-based manufacturing process allows the carbon devices to be integrated into millimeter scale silica-based templates without micro- or nanoassembly, facilitating commercialization. Furthermore, the carbon-based devices were designed to readily integrate into standard laboratory equipment, promoting broad utilization. Herein, a repeatable methodology for fabricating multifunctional, carbon-based micro- and nanofluidic devices as well as establishing relationships between parameters at each stage of fabrication and the final geometry, including diameter and wall thickness of the carbon structures, of the device is presented.

Commentary by Dr. Valentin Fuster
2017;():V010T13A019. doi:10.1115/IMECE2017-72027.

Power semiconductor devices such as MOSFET/IGBT and PiN diodes are widely used as basic components for supporting infrastructure in the field of electronics, including in power conversion, industrial equipment, railways, and automobiles. Recently, increasing attention has been paid to silicon carbide (SiC) as a wide-band-gap semiconductor suitable for use in power devices with low loss and high breakdown voltage. However, basic knowledge of the material properties and reliability of SiC devices, and particularly the influence of mechanical stress on device characteristics, is still incomplete. In this paper, we evaluated the effect of mechanical stress on the electrical characteristics of SiC devices. In order to investigate the effect of stress on the SiC device characteristic, we propose a simple evaluation method using four-point bending, which is a classical method capable of applying uniaxial stress to a device. With this method, we evaluated the stress in a SiC device using residual stress measurement by Raman spectroscopy and stress simulation based on the finite element method. Our proposed experimental method is as follows. First, the SiC device was bonded with AuGe solder to a metal plate [phosphor bronze; Young’s modulus: 105 GPa; Poisson’s ratio: 0.33; dimensions: 100 mm (W) × 12 mm (L) × 2 mm (T)], and aluminum wire (wire radius: 200 μm) was also bonded to the device. Second, the prepared device was placed on the specially designed four-point bending apparatus for mechanical stress experiments. Finally, the sample was bent in compression or tension in the in-plane direction by the four-point system. The SiC device was subjected to compression or tensile stress via the metal plate. The electrical characteristics of the SiC-MOSFET were measured with a curve tracer in our proposed system. IdVds characteristics changed linearly as stress was applied to the device. As a result, the on-resistance was increased by 7.6% by applying a tensile stress of 300 MPa and was decreased by 1.0% by applying a compressive stress of 100 MPa at room temperature, respectively. A power device circuit with multiple chips was also simulated by SPICE based on the experimental results to confirm the effects of stress on SiC devices in a power module. Simulated MOSFET model contains stress factors obtained from experimental results. The circuit was simulated by electro-thermal coupled analysis using a one-dimensional model of the electric circuit and thermal circuit constructed in SPICE. The results show that the proposed method is powerful simulation method for power device design.

Commentary by Dr. Valentin Fuster
2017;():V010T13A020. doi:10.1115/IMECE2017-72339.

There are strong needs for flexible and stretchable devices for the seamless integration with soft and curvilinear human skin or irregular textured cloths. However, the mechanical mismatch between the conventional rigid electronics and the soft human body results in many issues including contact breakage, or skin irritation. Due to the mechanical and electrical versatility of nanoscale forms, various nanomaterials have rapidly established themselves as promising electronic materials, replacing rigid wafer-based electronics in next-generation wearable devices. Here, we introduce a flexible, wearable bioelectronic system using an elastomeric hybrid nanocomposite, composed of zero-dimensional Carbon Black (CB) and one-dimensional Carbon Nanotubes (CNTs) and silver nanowires (AgNWs) in a polydimethylsiloxane (PDMS) matrix. Those materials were chosen due to their good electrical properties and their different length scale providing a continuous connection in the flexible PDMS matrix. To achieve a homogeneous dispersion, these nanomaterials were mechanically mixed in PDMS under shear flow using an overhead mixer. A hybrid nanocomposite membrane with dimensions of 15 mm diameter was then prepared by replica molding process. The electrical properties of the nanocomposite were measured over 5, 10 and 15hrs mixing time to investigate the point of electrical stability of the electrode and the electrical performance during EMG signal measurement. This soft nanocomposite, laminated on the skin, enables highly sensitive recording of electromyograms.

Commentary by Dr. Valentin Fuster

Micro- and Nano-Systems Engineering and Packaging: General Topics of MEMS/NEMS

2017;():V010T13A021. doi:10.1115/IMECE2017-70508.

Taking advantages of high stiffness, fast response, high-bandwidth as well as large pushing force capability, piezoelectric stack actuators have been widely used in the fields of high speed nano-positioning stages and precision systems. An inevitable disadvantage of piezoelectric actuators is that they are highly intolerant to shear and tensile forces. During high speed scanning operations, the inertial forces due to the effective mass of the stage may cause the actuators to withstand excessive shear or tension forces. To protect the actuators, preload is often applied to compensate for these forces. Flexures have been used to supply preload to the piezoelectric stack actuators in many high-speed nano-positioning stages. Nevertheless, for nano-positioning stages with stiff flexures, it is a difficult job to displace the flexures and slide the actuators in place to preload them. This paper proposed a novel preloading nano-positioning stage which allows the piezoelectric stack actuator to be preloaded and mounted easily without obviously reducing the stiffness and speed of the nano-positioning stage. A preloading nano-positioning stage is designed and the flexible hinge and piezoelectric stack actuator of the stage are analyzed. The stiffness and resonance frequency of flexible hinge and optimal preload for the proposed stage is obtained by kinetics analysis. In order to verify the effectiveness of preloading nano-positioning stage, an online test system is established. The system mainly composed by a force sensor module, a capacitive sensor module and the preloading nano-positioning stage. A force sensor is applied between piezoelectric actuator and flexible hinge which can directly measure the preload in real time. The displacement of the flexible hinge is measured by a capacitive sensor to evaluate the positioning accuracy. Experiments are conducted, and the results demonstrate the effectiveness of the proposed approach.

Topics: Actuators
Commentary by Dr. Valentin Fuster
2017;():V010T13A022. doi:10.1115/IMECE2017-71092.

Electrostatic comb-drive actuators in electrolytes have many potential applications, including characterizing biological structures. Maximizing the utility of these devices for such applications requires a model capable of accurately predicting their behavior over both micron and submicron scales of displacement. Classic circuit models of these systems assume that the native oxide is a pure dielectric, and that the ion concentration of the bulk electrolyte is constant. We propose augmented models that separately address these assumptions, and analyze their ability to predict the displacement of the electrostatic actuators in electrolytic solutions. We find that the model which removes the assumption that the native oxide is a pure dielectric most accurately predicts comb-drive actuator behavior in electrolytes.

Commentary by Dr. Valentin Fuster
2017;():V010T13A023. doi:10.1115/IMECE2017-71394.

This paper presents design, simulation, and experimentation of a novel Micro-electromagnetic vibration energy harvester based on free/impact motion. Power harvesting is simply achieved from relative oscillation between a permanent magnet allowed to move freely inside a tube-carrying electrical coil with two end stoppers and directly connected to the vibration source. The proposed harvester with free/impact motion shows a non-resonant behaviour in which the output power continuously increase with the input frequency and/or amplitude. In addition, the allowable free motion permits significant power scavenging at low frequencies. Hence, the proposed harvester is well suited for the applications involved variable large amplitude–low frequency vibrations such as human-powered devices. A nonlinear mathematical model of the proposed harvester including electromagnetic and impact characteristics is derived and used further for a case study model prediction. A unique way of oscillation is observed, in which four modes of magnet/tube relative motion appear over the range of exciting amplitudes and frequencies. Two experiments are conducted on different fabricated prototypes. The first shows the effect of different magnet shapes on the harvesting performance, and the second is carried out to investigate the performance of two different size prototypes with variable large amplitude-low frequency vibrations. A harvester with cylindrical total size of D9×L12 mm can generate RMS power of 71.8μW at (2.5 Hz and 5.2 m/s2), and 113.3μW at (3.33 Hz, and 12.38 m/s2). Another of D7×L12 mm size can generate RMS power of 28.4 μW at (2.5 Hz and 5.2 m/s2), and 82.9 μW at (3.33 Hz, and 12.38 m/s2). Comparison with some previously fabricated low frequency energy harvesters is made which shows the advantageous of the new harvester in size minimization as well as the significant power raise with the input amplitude.

Commentary by Dr. Valentin Fuster

Micro- and Nano-Systems Engineering and Packaging: Micro and Nano Devices

2017;():V010T13A024. doi:10.1115/IMECE2017-70388.

A new type tactile sensor with spatial resolution less than 1 mm and the minimum pressure sensitivity less than 10 kPa was proposed by applying MWCNTs (Multi-Walled Carbon Nanotubes). The sensor was embedded into a highly deformable flexible substrate (PDMS: Polydimethylsiloxane) and the obtained gauge factor of the developed sensor was about 5.

Since the electronic properties of MWCNTs vary drastically depending on their deformation under mechanical stress, it is important to make appropriate aspect ratio of MWCNTs for improving their stress-sensitivity. The aspect ratio of MWCNTs are mainly dominated by their growth condition such as the average thickness of catalyst layer, growth temperature, pressure of resource gases and so on. Thus, the optimum growth condition was investigated for forming the MWCNTs with high aspect ratio, in other words, high pressure sensitivity. In addition, in this study, the authors fabricated high quality carbon nano-materials to develop highly sensitive strain sensor. A thermal CVD synthesis process of MWCNTs was developed by using acetylene gas. After the synthesis of MWCNTs, flexible isolation material (PDMS) was coated around the grown MWCNT. Then, the interconnection film was deposited by sputtering. After that, PDMS was coated again to fabricate an upper protection layer. Finally, the bottom interconnection layer was sputtered and patterned. The change of the electrical resistance of the grown MWCNTs was measured by applying a compression test in the load range from 0 to 10 mN. It was found that the electrical resistance of the MWCNTs bundle increased almost linearly with the applied compressive load and this sensor showed the high load sensitivity of 10 mN that is higher than human fingers.

Commentary by Dr. Valentin Fuster
2017;():V010T13A025. doi:10.1115/IMECE2017-71639.

A ceramic-based micromodel was fabricated with batching of green alumina ceramics mixed with polymer binders, extrusion of the green alumina tapes, and hot embossing of the green tapes with a metal mold. The metal mold fabricated using optical lithography of SU8 and electroforming of nickel contained 2.5D pore network geometry in 13 layers of a rock, Boise sandstone. The hot embossing process enabled the generation of the pore network geometries with a minimum feature size of 25 μm and for distinct formation of the 13 layers of the 2.5D pore geometry of the rock. The green ceramic micromodels were processed with solvent extraction, thermal debinding, and sintering. The sintered micromodels showed significant shrinkages at all directions of the micromodels, which were 17.6% in x, 17.5% in y, and 14.6% in z. The sintered, 2.5D rock-based ceramic micromodel was capped with a thin glass cover slide and used for flow visualization with a fluorescent dye and fluorescent nano-particles. The dye-filled micromodel showed good flow connectivity and fluorescence signal intensity dependence on depth. It was observed that the peak particle concentration close to the observation window and gradual decrease in particle concentration along the depth. The higher velocities were measured in the low flow resistance region with velocity variations along the depth. The microfabricated 2.5D ceramic micromodels will allow resistance to harsh experimental conditions such as high temperature and pressure, and opportunity for investigation of the complex flow patterns in 3D.

Commentary by Dr. Valentin Fuster
2017;():V010T13A026. doi:10.1115/IMECE2017-71998.

This paper updates on the recent development of the novel Solid State Inflation Balloon (SSIB), a simple, reliable, low-cost, non-propulsive deorbit mechanism for the full range of small satellites, defined by NASA as less than 180 kg. It aims to focus on the recent demonstration, for the first time, inflation of a ∼10 cm sized balloon in a vacuum chamber. Small satellites typically rely on aerodynamic drag to deorbit within the FAA’s 25 year requirements. The SSIB will enhance aerodynamic drag by inflating a balloon at the end-of-life of a satellite mission. This technology will provide a scalable and non-existing capability, low-cost deorbit, for applications in the full-range of smallsats, from CubeSats to MicroSats. The SSIB system is composed of three major components: a Micro-Electro-Mechanical Systems (MEMS) Solid-State Gas Generator (SSGG) chip, a balloon structure made of thin film compatible with space environment (i.e. Mylar, Kapton, or Teflon), and a sub-system package suitable for spacecraft integration. The SSGG is composed of a 2D addressable array of sodium azide (NaN3) crystals, confined by Su-8 wells, on a glass substrate. Current versions include 2×2 and 8×8 arrays designed for a full range of small satellites. Under each well is a resistive heater and when heated to above 350 °C, the NaN3 spontaneously decomposes to generate N2 gas in time scales on the order of 10 milliseconds. Each well is designed with a typical volume of 10–15 m3 to 10−6 m3 of NaN3 (i.e. 1,500 μm × 1,500 μm × 150 μm on the larger end of the spectrum). The SSIB system is low power (∼1 W per well for less than 10 seconds) and have low mass (∼100 grams, where mass is dominated by the size of the required balloon). Initial simulations have shown that the SSIB with balloons of 1 m2 cross-section can deorbit small satellites from above 1000 km well within 25 years.

Commentary by Dr. Valentin Fuster

Micro- and Nano-Systems Engineering and Packaging: Microfluidics 2017 Microfluidics in Micro- and Nanosystems

2017;():V010T13A027. doi:10.1115/IMECE2017-70161.

The work presented here is motivated by the recent growing interest in using additive manufacturing to fabricate micro-channels networks. Distorted shapes and rough geometries influence hydrodynamic characteristics of micro-channels by increasing their flow resistance and pressure drop or altering wall shear stresses inside them. Since geometric conformity and shape fidelity of micro-channels networks are greatly influenced by manufacturing process, this work is focused on dimensional characterization of micro-channels fabricated using additive manufacturing. In this work, circular and rectangular cross-section micro-channels are 3D printed. Shapes and dimensions of 3D printed micro-channels are examined using Scanning Electron Microscope (SEM) imaging. In this work, 500 μm diameter and 200 μm square transparent PolyLactic Acid (PLA) micro-channels are 3D printed with average errors 0.25% and 1.65%, respectively. SEM images confirmed geometric conformity and shape fidelity of the 3D printed circular and rectangular cross-section micro-channels. Statistical analysis is performed on multiple prints to verify reproducibility and shape conformity. Results show that factors such as printing direction play essential role in the shape conformity and geometric fidelity of the micro-channels. Although 3D printing is a promising route for attaining micro-channels there are still significant improvements that can be made to the precision of the printer in the XY plane for printing small geometric figures. This improvement will likely come as the printing technology and software both improve to allow the operator more control over the outcome of the print. Additionally, new 3D printing materials may open the gate for new applications in different fields such as thermal management and microfluidics.

Commentary by Dr. Valentin Fuster
2017;():V010T13A028. doi:10.1115/IMECE2017-70632.

This paper presents the analytical solution of a combined electroosmotic/pressure driven flow of three viscoelastic immiscible fluids in a parallel flat plate microchannel. The mathematical model is based in the Poisson-Boltzmann equation and Cauchy momentum conservation equation. In the steady state analysis, we consider that the three fluids are electric conductors and obey to the simplified Phan-Thien-Tanner rheological model; therefore, different conditions at the interface between the fluids as electric slip, surface charge density and electro-viscous stresses balance are discussed in detail. Results show the transport phenomena coupled in the description of the velocity profiles, by the analyzing of the dimensionless parameters obtained, such as: the electric slips, the electric permittivities ratios, the surface charge densities, the zeta potentials at the walls, the interfaces positions, the viscosity ratios, the viscoelastic and electrokinetic parameters, and the term involving the external pressure gradient. Here, the presence of a net electric charges balance at the interface, breaks the continuity of shear viscous stresses, modifying the flow field; hence, for the established electric conditions at the interface through the values of the electric slips and the surface charge densities, play a role like a switch on the flow behavior. This investigation extends the knowledge about the techniques on the control of immiscible non-Newtonian fluids in microescale.

Commentary by Dr. Valentin Fuster
2017;():V010T13A029. doi:10.1115/IMECE2017-70677.

Mature red blood cell (RBC) consists of cytoplasm, mainly normal hemoglobin (HbA) within a plasma membrane. In sickle cell disease, abnormal sickle hemoglobin (HbS) molecule polymerizes and forms into rigid fibers at low oxygen tension, which contributes to variation in the biophysical properties of sickle cells from healthy RBCs. This paper presents an electrical equivalent circuit (EEC) model of sickle cell that considers the phase transition of oxy-HbS solution to deoxy-HbS polymers. Briefly, we model the oxy-HbS solution following healthy RBCs using a resistor and deoxy-HbS fibers as a capacitor. To validate the model, electrical impedance measurements of cell suspensions for normal RBCs and sickle cells are performed, using a multi-channel lock in amplifier in the frequency range of 1 kHz to 10 MHz in a customized microfluidic chamber. Quantitative measurements of the classical components of EEC model are extracted using the developed EEC sickle cell model, allowing us to better understand the biophysics of cell sickling event in sickle cell disease.

Topics: Circuits
Commentary by Dr. Valentin Fuster
2017;():V010T13A030. doi:10.1115/IMECE2017-71190.

In this study, we present a 1D method to predict the droplet ejection of a drop-on-demand (DoD) inkjet which includes the drop breakup, coalescence, and the meniscus movement at nozzle orifice. A simplified 1D slender-jet analysis based on the lubrication approximation is used to study the drop breakup. In this model, the free-surface (liquid-air interface) is represented by a shape function so that the full Navier-Stokes (NS) equations can be linearized into a set of simple partial differential equations (PDEs) which are solved by method of lines (MOL). The shape-preserving piecewise cubic interpolation and third-order polynomial curve are employed to merge approaching droplets smoothly. The printhead is simplified into a circular tube, and a 2D axisymmetric unsteady Poiseuille flow model is adopted to acquire the relationship between the time-dependent driving pressure and velocity profile of the meniscus. Drop breakup and meniscus movement are coupled together by a threshold of meniscus extension to complete a full simulation of droplet ejection. These algorithms and simulations are carried out using MATLAB code. The result is compared with a high fidelity 2D simulation which was previously developed [10], and good agreement is found. This demonstrates that the proposed method enables rapid parametric analysis of DoD inkjet droplet ejection as a function of nozzle dimensions, driving pressure and fluid properties.

Topics: Simulation , Drops
Commentary by Dr. Valentin Fuster
2017;():V010T13A031. doi:10.1115/IMECE2017-71251.

Due to the high surface area to volume ratios leading to intensified heat and mass transfer rates, microreactors have been subject of interest for some time. Liquid-liquid two-phase flow is a very common phenomenon in microchannels. During the scale-up using a numbering-up approach, rectangular and square microchannels are preferred to circular microchannels in terms of easier integration of the former with a less volume. Therefore, liquid-liquid two-phase flow in non-circular microchannels has been investigated recently. However, there are still gaps in the fundamental understanding of liquid-liquid two-phase flow, such as the effect of inlet junctions or arrangements on flow patterns in non-circular microchannels. The present work aims to study the effect of inlet arrangements on liquid-liquid two-phase flow dynamics and flow patterns of square glass microchannels. In this paper, oil is used as the dispersed phase and de-ionized water is used as the continuous phase. The special inlet arrangement in the cross-junction is compared to these common inlet arrangements of T-junction and cross-junction square microchannels. The effect of the inlet continuous phase velocity on the slug length is studied. Then, the slug lengths with the same inlet velocities of the three inlets and equal velocities of the two phases are carried out, respectively. Meanwhile, typical liquid-liquid flow pattern transitions are achieved at specific conditions. Finally, a special phenomenon without the droplet flow pattern is introduced, due to introduction of the novel inlet arrangement.

Commentary by Dr. Valentin Fuster
2017;():V010T13A032. doi:10.1115/IMECE2017-71285.

Contemporary Photonic Integrated Circuit (PIC) packages within the communications network infrastructure have reached a thermal limit. Integrated packages involving microfluidic channels are an appealing development to improve the thermal design of future PIC packages, to significantly improve the removal of heat fluxes in order to sustain the expected enhanced data traffic growth. The Thermally Integrated Smart Photonics Systems (TIPS) project aims to develop and demonstrate a thermally enabled integrated platform that is scalable, to meet the predicted data traffic demands. Full system integration requires an integrated pumping solution, therefore a primary heat exchanger that can deliver the required thermal performance with a low pressure drop (ΔP) is needed. A channel containing a single array of cylindrical posts offers a low pressure drop, similar to a large hydraulic diameter minichannel. Local destabilization of the flow would provide heat transfer enhancement. In particular, non-Newtonian fluids have been shown to exhibit significant mixing in such configurations. Micro Particle-Image Velocimetry (μPIV) measurements were taken for Newtonian and viscoelastic fluids within this channel. Instabilities associated with the viscoelastic fluid were recorded immediately upstream of the post array. This flow exhibited almost a four-fold increase in mixing at comparable flow rates to the Newtonian fluid tested. This suggests that the Nusselt number enhancement associated with such flows could increase the heat transfer rates quite significantly in microchannels containing obstructions.

Topics: Cooling , Photonics
Commentary by Dr. Valentin Fuster
2017;():V010T13A033. doi:10.1115/IMECE2017-71892.

Deterministic lateral displacement (DLD) is a common name given to a class of continuous microfluidic separation devices that use a repeating array of pillars to selectively displace particles having a mean diameter greater than the critical diameter (Dc). This Dc is an emergent property influenced by pillar shape, size, and spacing, in addition to the suspending fluid and target particle properties. The majority of previous research in DLD applications has focused on the utilization of laminar flow in low Reynolds number (Re) regimes. While laminar flow exhibits uniform streamlines and predictable separation characteristics, this low-Re regime is dependent on relatively low fluid velocities, and may not hold true at higher processing speeds. Through numerical modeling and experimentation, we investigated high-Re flow characteristics and potential separation enhancements resulting from vortex generation within a DLD array. We used an analytical model and computational software to simulate DLD performance spanning a Re range of 1–100 at flow rates of 2–170 μL/s (0.15–10 mL/min). Each simulated DLD array configuration was composed of 60 μm cylindrical pillars with a 45 μm gap size. The experimental DLD device was fabricated using conventional soft lithography, and injected with 20 μm particles at varying flow rates to observe particle trajectories. The simulated results predict a shift in Dc at Re > 50, while the experimental results indicate a breakdown of typical DLD operation at Re > 70.

Commentary by Dr. Valentin Fuster
2017;():V010T13A034. doi:10.1115/IMECE2017-72272.

Understanding the transport details around a microparticle in confined microchannel geometry is of importance in many microfluidics-based applications such as cell/ particle manipulation and separation. Despite of numerous studies contributed in the past decade, the micro flow structure induced by the moving particle is still not quantitatively measured in experiments. In this paper, we demonstrate direct measurement of the fluid flow around a single particle traveling in a confined microchannel based on the micro particle image velocimetry technique (μPIV). In the experiments, the straight polydimethylsiloxane (PDMS) microchannel was fabricated by the standard soft-lithography technique with 100 μm height, 60 μm width and 60 mm length. The polystyrene microparticles with 20 μm diameter were employed to travel in the microchannel and induce micro flows, while smaller fluorescent particles with 1μm diameter were used as seeding particles to indicate the local velocity. After being injected in the microchnnel with water, the microparticle with 20 μm diameter quickly reached its hydrodynamic equilibrium positions, which located on the horizontal symmetry plane of the microchannel, and got captured by the μPIV system together with seeding particles. By analyzing the motion of seeding particles, the time-averaged local flow vectors, velocity fields, vortex structures and fluid streamlines were quantitatively measured under different Reynolds numbers. The proposed experimental setup can serve as a basic platform to investigate the transport phenomenon of microparticles traveling in confined flow. The quantitatively measured flow structure can also be used for model validation by other researchers.

Commentary by Dr. Valentin Fuster
2017;():V010T13A035. doi:10.1115/IMECE2017-72598.

The prediction of leak rate through porous gaskets for different gases based on test conducted on a reference gas can prevent bolted joint leakage failure and save the industry a lot of money. This work gives a basic comparison between different gas flow models that can be used to predict leak rates through porous gasket materials. The ability of a model to predict the leak rate at the micro and nano levels in tight gaskets relies on its capacity to incorporate different flow regimes that can be present under the different working conditions. Four models based on Navier-Stokes equations and incorporate the boundary conditions of the appropriate flow regime considered. The first and second order slip, diffusivity and molecular flow models are used to predict and correlate leak rates of gases namely helium, nitrogen, SF6, methane, argon and air passing through three frequently used nanoporous gasket materials which are flexible graphite, PTFE and compressed fiber.

The methodology is based on the determination experimentally of the porosity parameter (N and R) of the micro channels assumed to simulate the leak paths present in the gasket using helium as the reference gas. The predicted leak rates of different gases at the different stresses and pressure levels are confronted to the results obtained experimentally by measurements of leak rates using pressure rise and mass spectrometry techniques. The results show that the predictions depend on the type of flow regime that predominates. Nevertheless the second order slip model is the one that gives better agreements with the measured leaks in all cases.

Topics: Gas flow , Gaskets , Leakage
Commentary by Dr. Valentin Fuster

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