bluuebunny/crossref_metadata_2025 huggingface dataset:
Modeling the Cooling Process Path of a Dehumidifying Coil Under Frosting Conditions
Authors: Mago P. J. , Sherif S. A.
Published: November 2021

Whenever humid air comes in contact with a cooling coil whose temperature is below both the dew-point of water vapor in air and the freezing point, frost will form. The nature of the frost forming on the coil will depend to a large measure on the psychrometric conditions prevailing inside the freezer and whether the air around the coil is subsaturated or supersaturated. Psychrometric theory and the apparatus-dew-point calculating procedure assume that the cooling process path as the air passes through the coil is a straight-line on the psychrometric chart. The actual path is however a result of a much more complex series of processes and is therefore a curve. While researchers have calculated the actual process path on a dehumidifying coil, none has attempted to do the same for a frosted, multi-row coil. It is believed that determining the actual conditions leaving a given row in a multi-row freezer coil is a crucial step in identifying the coil location in the vicinity of which the transformation from the subsaturated zone to the supersaturated zone occurs. This will prove a key step in identifying a demarcation line between the unfavorable snow-like frost and the more traditional (and more favorable) frost formation patterns. Thus the objective of this paper is to calculate the cooling process path in an actual industrial-size finned-tube, multi-row coil utilizing experimentally derived data and correlate the shape of the path with the prevailing psychrometric conditions in the freezer in the hope of identifying the demarcation line in question. The latter will be determined analytically and confirmed experimentally.
On Measuring Bubble Nucleation Temperature of Water/Methanol Mixtures Using Ink-Jet Printer Technology
Authors: Avedisian C. T. , Osborne W. S. , McLeod F. D.
Published: November 2021

The bubble nucleation temperature of water/methanol mixtures is measured using the fast transient process of thermal ink-jet printer technology. The heater element is placed in a dynamic bridge circuit coupled with an instrumentation amplifier to measure the change in resistance of the heater as a programmed voltage is applied across the bridge. An inflection point in the evolution of resistance signals bubble nucleation. A separate calibration relates resistance to average heater temperature.

The results show that the nucleation temperature increases as the power input to the bridge increases for a given concentration. The heating rates are extremely high, in some cases reaching over a quarter billion degrees per second. As methanol concentration increases, the nucleation temperature decreases. It was difficult to measure the nucleation temperature at high methanol dilution because the difference between liquid and vapor thermal conductivity decreases as methanol concentration increases for a given temperature. The nucleation temperatures are successfully correlated with a generalized corresponding states theory.
An Integrated Macro- and Micro-Scale Model for Detached Solidification in a Bridgman Growth System
Authors: Zhang H. , Larson D. J. , Chen T. H. , Xu J.
Published: November 2021

Prior space experiments have suggested that the defect (twin and dislocation) density can be dramatically reduced if the crystal is grown without wall contact. Techniques have been proposed to promote wall detachment during solidification by Larson, Duffar, and Wilcox. In this paper, we adopt an ampoule with a soft-finned carbon inner wall, which can arrange for growth essentially free from wall contact. An integrated numerical model for detached solidification has been developed to combine a global heat transfer model of a Bridgman system with a meniscus model near the wall. The global model accounts for heat transfer in a multiphase system (solid, liquid and gas), convection in the melt, and interface dynamics. The meniscus model accounts for meniscus dynamics over a finned structure, and a force balance at the three-phase boundary. The effects of the finned carbon wall on the temperature gradients and the interface shape will be investigated. The integrated model will be used to design apparatus and find the optimal geometry for detached solidification of CdTe growth in space and on the ground.
Micropumping by Electrowetting
Authors: Kim Chang-Jin “CJ”
Published: November 2021

This paper introduces the recent effort to use surface tension in MEMS, especially, to use electrowetting for efficient pumping in microfluidics. Importance of surface tension in microscale is explained, and examples of utilizing it to design microdevices are presented. Development of several devices employing different types of electrowetting is explained. Empowered by the efficient pumping by electrowetting microactuation, a programmable digital microfluidic circuit chip is proposed.
Mass Quality, Void Fraction, and Slip Ratio in Bulk Flow Boiling
Authors: Collado Francisco J.
Published: November 2021

New general, multidimensional transport equations for two-phase flow have been recently proposed by the author. The new theory is based on a quite simple idea namely, if the phases have different velocities, it is impossible that they cover the same distance in the same time. From this quite different point of view, new mass and energy balances for one-dimensional, steady, two-phase flow have been already presented. In this paper, after briefly reviewing the key points of the new balances, the prediction of the vapor-liquid velocity ratio (the slip) and the vapor void fraction for bulk flow boiling is analyzed with the help of the new approach. The new expressions are well compared with the bulk flow boiling data for a horizontal pipe from the Cambridge Project.
Numerical Simulation of Capillary-Tube Behaviour Working With Pure and Mixed Refrigerants Under Adiabatic and Non-Adiabatic Flow Conditions
Authors: García-Valladares O. , Pérez-Segarra C. D. , Oliva A.
Published: November 2021

A detailed numerical method for analysing the thermal and fluid-dynamic behaviour of capillary tube expansion devices working with pure refrigerants and mixtures has been developed by means of a one-dimensional analysis of the governing equations (continuity, momentum and energy). Metastable both liquid and two-phase regions have been taken into account.

The discretized governing equations are coupled using an implicit step by step method. In order to minimise computational cost, a special treatment has been implemented to solve the control volume that contains transition between regions and a special mesh distribution has been used. All the flow variables together with the thermophysical properties are evaluated at each point of the grid in which the domain is discretized. The numerical model allows analysis of aspects such as geometry, type of fluid, critical or non-critical flow conditions, metastable regions, adiabatic or non-adiabatic capillary tubes and transient aspects.

The accuracy of the detailed simulation model is demonstrated by comparison with experimental data from the technical literature for adiabatic capillary tubes and also for concentric capillary tube-suction line heat exchanger.
The Run-off Condition for the Non-Newtonian Rimming Flow
Authors: Fomin Sergei , Harkin-Jones Eileen , Watterson John , Raghunathan S.
Published: November 2021

Rimming flow on the inner surface of a horizontal rotating cylinder is investigated. Using a scale analysis, a theoretical description is obtained for steady-state non-Newtonian flow. Simple lubrication theory is applied since the Reynolds number is small and liquid film thin. Since the Deborah number is very small the flow is viscometric. The Weissenberg number, which characterizes the shear-thinning effect, maybe small or large. A general constitutive law for this kind of flow requires only a single function relating shear stress and shear rate that corresponds to a generalized Newtonian liquid. For this case the run-off condition for rimming flow is derived. Provided the run-off condition is satisfied, the existence of a continuous steady-state solution is proved. The rheological models, which show Newtonian behaviour at low shear rates with transition to power-law shear thinning at moderate shear rates, are considered. Numerical results are carried out for the Carreau and Ellis models, which exhibit the Newtonian behaviour near the free surface and power-law behaviour near the wall of the rotating cylinder.
Shape Factor in the Latent-Heat-Thermal-Energy-Storage Systems
Authors: Fomin Sergei
Published: November 2021

An approximate mathematical model of contact melting of an unfixed material in an elliptical capsule is developed. The main characteristic scales and non-dimensional parameters, which describe the principal features of the melting process, are found. Choosing the special heat flux distribution on the wall of the capsule allows us to derive a closed-form evolution equation for the motion of the solid, which also determines the melting rate. It is shown that the melting rate depends on the shape of the capsule. The elliptical capsules show higher rate of melting than the circular ones. The vertically elongated capsules provide more effective melting than the horizontally elongated ones, even though they have the same aspect ratio and vertical cross-sectional areas. The time required for complete melting can be achieved by the right choice of the shape of the capsule, which is specified by the value of the aspect ratio. This is especially important for the design of practical latent-heat-thermal-energy-storage systems.
The Effect of Run-Out on Design for Manufacturing in Micro-Machining Process
Authors: Lee Kiha , Ahn Sung-Hoon , Dornfeld David A. , Wright Paul K.
Published: November 2021

Micro-machining by mechanical machine tool, or micro mechanical machining, is an emerging fabrication technology that broadens applicable material ranges including metals and plastics. One of the problems in this micro machining, however, is relatively large run-out which is comparable to the diameter of tools. A series of experiments were conducted to identify Total Indicator Reading (TIR) and dynamic run-out of micro-machining on aluminum workpieces. Results presented in this paper indicate the ratio of run-out to tool diameter ranged between 2.2% and 10%. To compensate for the run-out in the design stage of micro features, a Java-based Design for Manufacturing (DFM) tool was developed. This tool can assist designers to design micro channels accurately considering the effect of run-out. Furthermore, the feasibility of micro-injection molding was examined with micro-machined channels. Micro-molded parts were made from ABS plastic showing negligible shrinkage from the molding process.
Evaluation of Chip Morphology in Hard Turning Using Constitutive Models and Material Property Data
Authors: Poulachon Gérard , Moisan Alphonse L. , Jawahir I. S.
Published: November 2021

Modelling of machining operations requires the use of constitutive relations which could represent as close as possible the material behavior in the primary and secondary zones. The knowledge of these behavior laws involves the use of different types of sophisticated mechanical tests which should provide with sufficient accuracy the material behavior for the relevant conditions of machining. In this paper, firstly, the flow stress of 100Cr6 (AISI 52100) bearing steel in its HV730 hardness state has been identified in order to assess the machinability in case of hard turning. With this, the dependence of the flow stress on strain, strain-rate and temperature, which poses significant difficulty, is presented. Secondly, the material machinability is evaluated with a shear instability criterion, enabling the prediction of chip formation with or without the shear localization. Quick-stop tests have been carried out on the bearing steel treated at different hardness values showing the chip formation variation. Micro-hardness tests performed on these quick-stop test samples show the effects of cutting temperature. A greater understanding of applied machinability is gained through this precise study of work material physical properties and behavior.
Extension of Oxley’s Analysis of Machining to Use the Johnson-Cook Material Model
Authors: Adibi-Sedeh Amir H. , Madhavan Vis , Bahr Behnam
Published: November 2021

The aim of the present work is to extend the applicability of Oxley’s analysis of machining to a broader class of materials beyond the hot rolled low-carbon steel used by Oxley and coworkers. The Johnson-Cook material model has been chosen to represent the mechanical properties of the material being machined as a function of strain, strain rate and temperature. Necessary changes have been made to Oxley’s analysis to make it self-consistent for this material model. A new approach has been introduced to calculate the pressure variation along the beta slip lines in the primary shear zone including the effects of both the strain gradient and the thermal gradient along the alpha lines. The shear force along the primary shear zone is calculated in a consistent manner using the energy dissipated in this zone. The thickness of the primary and secondary shear zones, the heat partition at the primary shear zone, the temperature distribution along the chip-tool interface and the shear plane angle are all calculated using Oxley’s original approach. Two constants are used to fine tune the model — the strain in the chip material at the chip tool interface (εint), and the ratio of the average temperature to the maximum temperature at the chip-tool interface (ψ).

The performance of the model has been studied by comparing its predictions with experimental data available in the literature for aluminum 2024-T4. It is found that the model accurately reproduces the dependence of cutting force as a function of depth of cut and cutting speed. The shear plane angle predicted is smaller than that observed in practice. It is also observed that the constant ψ needs to be very small, implying very little increase in the temperature along the chip-tool interface. The model is highly nonlinear in the constant C that relates the length of the primary shear zone to its thickness.
Investigation Into the Tube-Bending Process by Using Elastomer
Authors: Zeng Yuansong , Li Zhiqiang
Published: November 2021

A tube-bending process is presented in the paper, in which an elastomer is employed as an internal pressure transmitting medium. Finite element method is applied to simulate the forming process. Numerical results show that the internal pressure and the friction condition play an important part during the bending process. Experimental research was also performed. It is found that the numerical results are in good agreement with the experimental values, and an aluminum alloy tubular component with relative bend radius equal to 1 was manufactured without wrinkling and fracturing.
An Experimental Investigation of Necking in Thin Sheets
Authors: Tong Wei , Zhang Nian
Published: November 2021

Due to its simplicity in instrumentation and data analysis, uniaxial tensile tests are commonly used for determining the plastic stress-strain relation of a sheet metal. However, the tensile stress-strain data obtained using the standard procedure is valid only up to the moderate strain level just before the onset of diffuse necking in the specimen gage section. Once the diffuse necking starts, the plastic deformation of the specimen becomes increasingly non-homogenous within the necked region. Questions arise regarding the validity of extrapolating the uniaxial stress-strain data to very large strains when one analyzes the forming failure of the sheet metal. Here an experimental technique and the related application procedure for obtaining rate-dependent, anisotropic, tensile stress-strain data of sheet metals at large strains up to fracture are described. Detailed plastic strain mapping results of a tapered commercially pure titanium thin sheet specimen are presented to characterize necking of the thin sheet. A brief discussion of a hybrid experimental and numerical methodology for estimating the strain hardening, strain rate sensitivity, and plastic anisotropy of sheet metals at large tensile strains is given. Preliminary results on necking in aluminum alloys, copper alloys, and low-carbon steel thin sheets are also presented.
Formability Enhancement for Tailor-Welded Blanks Using Blank Holding Force Control
Authors: He Sijun , Wu Xin , Hu S. Jack
Published: November 2021

Tailor-welded blanks (TWB) are widely used for stamped auto panels because of their great benefits such as weight and cost reduction. However, the weld line in a tailor-welded blank causes serious concerns in formability because it induces material discontinuity and additional inhomogeneous stress/strain distribution. This paper proposes a blank holding force (BHF) control strategy to control the weld line movement, distribute the deformation more uniformly and improve TWB formability. The control methodology is developed based on a simplified 2-D sectional analytical model that estimates the stress/strain distribution and the required BHFs for each side of flange with dissimilar materials. The model can be further extended to 3-D by superimposing the 2-D sectional analysis results around the entire binder ring and thus determining required BHF for the whole panel. Finite element simulations are performed to study the effects of forming parameters on the weld line movement. Experiments have been conducted to verify the analytical model and partial finite element simulations. Both analysis and experiments demonstrated that a lower BHF should be applied on the thicker blank side to allow more metal to flow in for obtaining more uniform strain distribution. The proposed BHF control is proven to be a good solution to enhance TWB formability.
Plastic Deformation of a Perforated Sheet With Non-Uniform Circular Holes Along the Thickness Direction
Authors: Chen Fuh-Kuo , Lee Yi-Che
Published: November 2021

For a perforated sheet with circular holes, used in shadow masks, the diameter of the circular hole varies through the thickness, and the non-uniform circular holes are arranged in a triangular pattern. In order to simplify the analysis, a perforated sheet with equivalent circular holes of uniform diameter is proposed such that its plastic behavior is similar to that with the given non-uniform circular holes. In this study, a yield criterion is discussed for the perforated sheet with uniform circular holes by employing an equivalent continuum approach, which is then applied to examine the plastic deformation of the perforated sheet with non-uniform circular holes. The analytical results predicted by the theory, including those for the apparent yield stresses and strain ratios, are verified by the results obtained from the finite element analysis and also from experiments.
A New Forming Limit Criterion and Ductile Fracture Prediction in the Forging of Sintered Powder Preforms
Authors: Huang Cheng-Chao , Cheng Jung-Ho
Published: November 2021

The main purpose of this study is to investigate the forgability of sintered powder compacts, including the void evolution and fracture prediction in the forming process. A new ductile fracture criterion for porous media is developed based on the maximum principal strain energy per unit of volume. It demonstrates that the strain energy density is governed by the maximum principal stress in material. Fracture will occur as the accumulation of strain energy density reaches the critical value at that point.

Experiments and Finite element analysis were conducted to establish the models. The material properties of sintered porous preforms were obtained from both the uni-axial tension and compression tests. The finite element models were verified with experiments of upsetting under different frictional conditions. Studies show that the results by the new criterion are more compatible with the experimental data than other previous forms. In addition, voids lead to the degradation of the strength and workability of materials. Friction contributes to the non-uniformity of deformation and density variation that causes the workpiece to fracture.
The 2000 CASA/SME University Lead Award Winning Joint Engineering/Business Masters in Manufacturing Program at Penn State
Authors: Ruud Clayton O. , Hottenstein Michael P. , Winkelblech Cindy K.
Published: November 2021

A unique, new joint graduate program in manufacturing engineering and management, was introduced in the fall of 1996 at Penn State. It is an integrated two-semester academic program created at the request of, and with the cooperation of industry. The creation was a joint effort of faculty from the Colleges of Engineering and Business. The courses were all developed specifically for the program, are all required, and taken in lock-step by each class cohort. Faculty members from both colleges teach in the program, often with both being present in the classroom to provide continuous integration of course material. The students have backgrounds in business, engineering, science, and industry and are selected to provide diversity in each cohort class. The degree awarded is a Masters of Manufacturing Management (MMM).

This paper describes the founding principles and curriculum of the program and provides profiles of the five classes of students that have graduated.
Experimental Study of Forming Rene95 Alloy Parts by Laser Cladding
Authors: Deng Qilin , Hu Dejin , Pei Jingyu , Zhang Wenwu , Yao Y. Lawrence
Published: November 2021

In this paper, experimental study of forming metal parts by laser cladding Rene95 alloy powder was reported. The influence of main process parameters, such as laser power, scanning speed and laser beam diameter, on the thickness, width and the angle of the laser cladding track was investigated. The microstructures of laser cladding parts were studied and compared with those of common casting parts. The obtained Rene95 metal parts formed by laser cladding are dense and of high strength.
Laser-Assisted Machining of Reaction Sintered Mullite Ceramics
Authors: Rebro Patrick A. , Shin Yung C. , Incropera Frank P.
Published: November 2021

The present study focuses on the evaluation of the laser-assisted machining (LAM) of pressureless sintered mullite ceramics. Due to mullite’s low thermal diffusivity and tensile strength, a new method for applying laser power is devised to eliminate cracking and fracture of the workpiece during laser heating. The LAM process is characterized by means of cutting force and surface temperature measurements for a variety of operating conditions. Estimated material removal temperatures and the ratio of the feed force to the main cutting force are used to determine material removal mechanisms and regimes for brittle fracture and semi-continuous and continuous chip formation. Surface roughness and subsurface damage are compared for typical parts produced by LAM and grinding. Tool wear characteristics are investigated for variations in laser power, and hence material removal temperature, during LAM of mullite with carbide tools.
Residual Stress Reduction by Pulsed Magnetic Treatment
Authors: Klamecki Barney E.
Published: November 2021

Residual stress relief by pulsed magnetic treatment is attractive since the process is carried out at room temperature and magnetic fields that are easy to produce and control can be used. The extent of residual stress reduction due to a particular pulsed magnetic treatment was determined. Initially curved strip specimens were held flat to produce a known residual stress and then subjected to a pulsed magnetic treatment. Microhardness measurements before and after treatment and a mechanical model relating stress and indentation size were used to specify the change in residual stress due to pulsed magnetic treatment. Changes of stress near the surface of the specimens due to treatment were obtained. Reductions of residual stress of 4%–7% were obtained for the particular pulsed magnetic treatment used on lower initial stress level specimens. For a higher initial stress level stress reductions of 8%–13% were measured.
A Wafer Transfer Technology for MEMS Adaptive Optics
Authors: Yang Eui-Hyeok , Wiberg Dean V.
Published: November 2021

Adaptive optics systems require the combination of several advanced technologies such as precision optics, wavefront sensors, deformable mirrors and lasers with highspeed control systems. The deformable mirror with a continuous membrane is a key component of these systems. This paper describes a new technique for transferring an entire wafer-level silicon membrane from one substrate to another. This technology is developed for the fabrication of a compact deformable mirror with a continuous face sheet. A 1 μm thick silicon membrane, 100 mm in diameter, has been successfully transferred without using adhesives or polymers (i.e. wax, epoxy, or photoresist). Smaller or larger diameter membranes can also be transferred using this technique. The fabricated actuator membrane with an electrode gap of 1.5 μm shows a vertical deflection of 0.37 μm at 55 V. The proposed technique has the following benefits over those previously reported: 1) No post-assembly release process (e.g. using HF) is required, and no wax, photoresist, or epoxy is used for the transfer purpose 2) The bonded interface is completely isolated from any acid, etchant, or solvent, which ensures a clean and flat membrane surface. 3) It offers the capability of transferring wafer-level membranes over deformable actuators.
A New Assembly-Transferred Microwave Switch With Suspended CMOS-Compatible Coplanar Waveguides
Authors: Chen Jen-Yi , Huang Long-Sun , Chu Chia-Hua , Li I-Yin , Kuo Yao-Hui , Chang Peizen
Published: November 2021

The paper reports a new, transferred micromachined microwave switch on top of suspended transmission lines for high performance and Si-based CMOS compatibility. The micro assembly transfer technique is used to integrate functional complex structures of the mircomachined microwave switch and suspended coplanar waveguides. The electrostatically actuated torsional switch has been successfully driven in a low voltage of 17 volt. Furthermore, the resonance of its dynamic behavior is numerically calculated as 2.6 KHz. In summary, the new microwave switch with suspended Si-based coplanar waveguides presents low driving voltage, CMOS-process compatibility and potentially high transmission efficiency on a lossy Si-based substrate.
Micromechanical Clamps for Optical Fiber Packaging of High Aspect Ratio MEMS Devices
Authors: Beamesderfer Michael A. , Litcher Ed , DeVoe Don L.
Published: November 2021

This paper describes the design and characterization of monolithic clamping structures for mechanical packaging of optical fibers in optical MEMS devices. Both single crystal silicon and nickel LIGA components have been investigated [1,2]. Mechanical clamping methods for optical fiber integration were perused both for on-chip attachment as well as alignment-assist in conjunction with other packaging methods. Arrays clamps with normal clamping forces ranging from 3mN to 375mN were designed, fabricated and characterized. A detailed theoretical analysis of clamping force for each design is presented and compared to measured results from fabricated devices. The clamps were evaluated on their ability to maintain alignment under a range of mechanical and thermal loads. Four arrays of eight clamp sets with varying applied normal clamping forces were designed by varying the deflection of 10μm and 20μm cantilever beams, and arranged in single-clamp and double-clamp configurations. A 100μm moment arm, integrated into the clamp structure, permitted the cantilevers to be initially deflected by the inserted fiber face during the fiber channel population. The populated test clamp arrays were heated from ambient conditions to 55 degrees Celsius to assess their stability under thermal strain, and monitored with an integrated Fabry-Perot whitelight interferometer. The maximum induced axial misalignment did not exceed 3μm. In addition to current theoretical and experimental results, alternative mechanical fiber clamp designs for both silicon and nickel microfabrication are presented and analyzed.
Processing of Ceramic Tapes Into 3-D Shells and its Application to a Small Spherical Stepper Motor
Authors: Li Jun , Ananthasuresh G. K.
Published: November 2021

Low Temperature Co-fired Ceramic (LTCC) tapes (DuPont, 951 series), originally developed for monolithic packaging of interconnects and hybrid microelectronic circuitry, have been used in the last four years to develop a meso-scale integrated fluidic technology. The LTCC fluidic technology is shown to be versatile, inexpensive, fast, and free of packaging problems. The manufacturing basis for this technology is patterning of individual tapes, which are laminated and co-fired to create a layered 3-D structure. In this paper, we present another attractive facet of this technology by creating 3-D shell structures with a single layer of LTCC tape. The processing technique is illustrated with hemispherical and cylindrical shells that have internal 3-D conduits. A novel three degree-of-freedom spherical stepper motor is also presented as an application of an active device using magneto-statically actuated curved LTCC shells.
3 KHz Servo Bandwidth Demonstration by HDD Tracking Microactuator
Authors: Hirano Toshiki , White Matthew , Yang Xin H. , Semba Tetsuo , Shum Victor , Pattanaik Surya , Arya Satya , Kercher Dan , Fan Long-Sheng
Published: November 2021

A demonstration of a closed loop system with a 3 kHz 0 dB open loop crossover using a microactuator in an HDD is reported. An electrostatic rotational microactuator is placed between the suspension beam and the slider, and moves the slider relative to the suspension. A new suspension with extra leads that provide signal to the microactuator was also developed. These leads are electrically connected by a micro-scale solder-ball reflow process. The dual-stage servo experiment was carried out in an HDD and a 3 kHz servo bandwidth was achieved, which is more than twice as high as a conventional servo system. The error rejection function also shows that this dual-stage servo system has superior error rejection capability over the conventional VCM-only servo system. Simulation shows that the bandwidth can be as high as 44 kHz, if a continuous-time servo is used.
Microscale Liquid Impingement Cooling
Authors: Zhang Lian , Wang Evelyn N. , Koch Jon D. , Liu Jonathan T. C. , Koo Jae-Mo , Jiang Linan , Goodson Kenneth E. , Santiago Juan G. , Kenny Thomas W.
Published: November 2021

Impingement cooling is an attractive method for individual IC cooling because of the uniformity and high values of the expected heat transfer coefficient. This paper presents spatially-averaged temperature measurements for DI water impingement from single micro jets with diameters smaller than 50 μm. The jets are circular orifices plasma etched into silicon. A heater chip is fabricated to simulate a high power IC while simultaneously measuring the temperature distribution around the impingement region. A hydrodynamic model is proposed for determining the pressure drop associated with jet formation. With a single 50 μm diameter DI water jet at 3.5 ml/min flow rate, up to 45 W/cm2 heat flux has been removed with 80 °C chip temperature rise. This research provides the first study of microscale liquid impingement cooling down to 14 μm diameter jets.
A Thermomechanical Model for Adhesion Reduction of MEMS Microcantilevers
Authors: Rogers James W. , Mackin Thomas J. , Phinney Leslie M.
Published: November 2021

We present a model for reducing adhesion in MEMS structures using laser heating and compare the model to experimental results. Using a fracture mechanics model, the interface between the stiction-failed microcantilever and the substrate is treated as a crack, and the energy release rate is calculated using elastic theory. In order to include the effect of laser irradiation of the microcantilevers, an associated thermal strain energy is included in the fracture model. As the beam peels, the free length reaches a critical value where the beam buckles, decreasing the energy of the system. The results of the model predict a temperature difference of 100 K is able to repair microcantilevers as long as 600 μm. Experiments are performed that demonstrate the peeling of stiction-failed beams from the substrate after laser irradiation as predicted by the thermomechanical model.
Design of MEMS Resonators for Tuning With Selective Polysilicon Deposition
Authors: Joachim Daphne , Lin Liwei
Published: November 2021

Variations in micromachining processes cause sub-micron differences in the size of MEMS devices, which leads to frequency scatter in resonators. A post-fabrication process was developed to tune the frequency of a comb-drive resonator by selectively adding polysilicon to the rotor. The resonator was designed using finite element simulations, to withstand the thermal stresses of the deposition process and have initial frequency in a desirable range. Experimental results show a permanent increase of 2.6% in the resonant frequency of a special comb-drive resonator after a deposition process time of 15 minutes.
Splitting a Liquid Droplet for Electrowetting-Based Microfluidics
Authors: Cho Sung Kwon , Moon Hyejin , Fowler Jesse , Kim Chang-Jin “CJ”
Published: November 2021

This paper deals with the physical analysis and the experimental verification of splitting a droplet in an open microchannel (i.e., in a gap between two plates) by electrowetting forces. We discovered there exist criteria beyond which the droplet simply cannot be split by controlling the electrowetting. Based on the criteria, we fabricated the testing devices where an electrowetting principle was used to split a liquid droplet and made the experimental verification for the criteria. The channel gap size, the droplet size, and the contact angle change by electrowetting are important parameters in splitting a droplet. The small channel gap enhances the necking of the droplet, helping the splitting process. Higher applied voltage induces larger change in contact angle and consequently enhances the splitting process as well. Most importantly, the droplet cannot be split if the channel gap is too large for the given droplet size and EWOD mechanism.
Operating Frequency of Thin Film NiTi in Fluid Media
Authors: Shin Daniel D. , Carman Gregory P.
Published: November 2021

For the present paper, the operating frequencies for thin film Nickel-Titanium (NiTi) shape memory alloy were investigated. The results thus far have shown that careful delivery of power to NiTi membrane increased the operating frequency by an order of magnitude. The method of power delivered to the membrane seemed to depend on the thermal conductivity of the fluid in contact. Stagnant air and mineral oil required shorter heating times and less power due to then-low conducting characteristics. De-ionized water on the other hand required greater power and longer heating time. Although heat dissipation to the surrounding was inevitable, it was determined that delivering large bursts of energy in a short heating time can minimize such loss. This way, more energy was used to heat the membrane rather than dissipating to the surroundings. While only 60Hz was measured using the thin film membrane, higher operating frequencies are achievable if power delivery to the membrane is carefully controlled.
Electrothermal Linear Micromotors Fabricated From Deep Reactive Ion Etching of Single Crystal Silicon
Authors: Maloney John M. , Schreiber David S. , DeVoe Don L.
Published: November 2021

Electrothermal linear motors with heights of 50 μm have been fabricated by using deep reactive ion etching (DRIE) on silicon-on-insulator (SOI) wafers. The motors are powered by V-beam thermal actuators that deflect laterally when current is applied. Synchronized arrays of actuators are used to position and clamp a slider through frictional contact only, improving positioning resolution. These high-aspect-ratio motors produce significantly larger forces than similar polysilicon electrothermal or electrostatic devices. Forces of 6.7 mN have been demonstrated at a voltage of 12 V, making these motors well suited for positioning compliant mechanisms. Motors measuring 2.5 mm by 2.1 mm in die area have been run at speeds of up to 1 mm/s over a range in excess of 2 mm.
Micromachined Fabry-Perot Interferometers for the Demodulation of Fiber Optic Strain Sensors
Authors: Rosenberger Frederick F. , Schreiber David S. , DeVoe Don L.
Published: November 2021

Two types of micromachined Fabry-Perot interferometers have been developed to serve as adjustable read-out interferometers for an optical fiber strain sensor system. The fabricated micromirror serves as one reflective surface of the Fabry-Perot cavity, with the cleaved, coated end of the input optical fiber acting as the second surface. Electrostatic and thermal actuators allow adjustment of the cavity spacing. Due to the particular system requirements, the micromotors used to position the mirror must provide large displacements (over 50μm) with sub-micron positioning accuracy. Two different embodiments of the interferometer design, including integrated micromotors, have been achieved. The first design, fabricated using the Cronos MUMPs 2.5-layer polysilicon process, consists of a pop-up mirror mounted on a slider that is positioned in front of the fiber by an electrothermal stepper motor. The second design, fabricated using Deep Reactive Ion Etching (DRIE) of single crystal silicon, uses a bulk etched silicon mirror that is positioned in front of the fiber by an electrostatic comb drive. Design, fabrication, and characterization of the interferometers are discussed.
Development of a Program for Predicting Residual Stress Distribution in Multi-Stacked Film
Authors: Choi Hyeon Chang , Park Jun Hyub , Park Yong Soo
Published: November 2021

The mean stresses of the single and multi-stacked film are experimentally investigated. After stacking several layers on a wafer, we measure the curvature on the wafer. Followed by peeling each layer stacked, we measure the curvature on the wafer, again. Mean residual stresses are calculated from radiuses of the curvatures using the Stoney’s equation[1]. Microcantilever beams is constructed by removing substrate and the deflection at the end of a beam is measured.

Finite element method for determining residual stress distribution in multi-stacked films with a multi-step doping process is studied for use in micromachining applications. We propose a finite element program for residual stress analysis (RESA) in multi-stacked polysilicon film. The distribution of residual stress field in multi-stacked films is predicted using RESA. And it is established for the prediction method determining the deflection in a cantilever beam using finite element method (FEM).
Through-Wafer Electrical Interconnects for MEMS Sensors
Authors: Chandrasekaran Venkataraman , Chow Eugene M. , Kenny Thomas W. , Nishida Toshikazu , Sheplak Mark
Published: November 2021

The fabrication and characterization of p-type silicon electrical through-wafer interconnects (pETWI) on a silicon wafer is presented. Together with previously developed n-type ETWI [1], the pETWI enables complementary ETWI (CETWI) for maximum flexibility of through-wafer interconnects for MEMS sensors and semiconductor devices. Deep reactive ion etching using the Bosch process is employed to create high aspect ratio 20 μm vias through the wafer. The interconnects are electrically isolated from the bulk silicon substrate by a 2 μm thermal oxide layer. Electrical conduction is achieved by depositing several layers of boron-doped polysilicon. Details of the fabrication process as well as results of the pETWI characterization are presented. Interconnects with various polysilicon doping concentrations were fabricated to investigate the effect on the resistance, capacitance and noise. Average resistance values between 10 Ω and 14 Ω were obtained for each interconnect depending on the doping levels. This resistance is suitable for many MEMS applications. High frequency capacitance versus voltage (C-V) characteristics and the noise power spectral density (PSD) were also measured.
Metal-Induced Laterally Crystallized Polycrystalline Silicon for Micro-Systems: Mechanical and Etching Characteristics
Authors: Wang Mingxiang , Yeung Wan Lap , Zohar Yitshak , Wong Man
Published: November 2021

It is determined that for metal-induced laterally crystallized (MILC) polycrystalline silicon (poly-Si), the mechanical and etch properties compare favorably with and the sensing and electrical properties are better than those of conventional low-pressure chemical vapor deposited (LPCVD) poly-Si. The etching characteristics of MILC poly-Si in tetra-methyl ammonium hydroxide (TMAH) solution have been studied. A unified model based on preferential grain boundary (GB) etching has been proposed to explain the etching behavior of poly-Si in TMAH.
Fabrication of Micropipes for Optical Interconnects Using Electroless Processes
Authors: Cheng Yu-Ting , Sambucetti Carlos , Teh K. S.
Published: November 2021

A novel process for low cost fabrication of metallic micropipes has been successfully developed. This method requires only selective surface activation of a single mode optical fiber followed by electroless plating. Concentrated HF and sulfuric acid solutions are used to remove the glass core and the polymer buffer of the fiber with a rate of 500 μm/hr and 500 μm/min respectively. These micropipes can have different inner diameter (i.d.) such as 125 or 250 μm, depending on the size of the optical fiber, and hence they are very suitable for high precision splicing of single mode optical fibers as well as for optical switches used in fiber-optical systems. The fabrication process holds great promise to evolve into an inexpensive manufacturing process for mass production of micropipes and also it can be integrated with Silicon Optical Benches metallurgical techniques.
A Novel Testing Machine for Characterization of Materials for MEMS Applications
Authors: Gudlavalleti Sauri , Anand Lallit
Published: November 2021

We have developed a novel uniaxial testing machine for testing small samples in the load range 25 μN – 1.5 N and specimen size/displacement range μm - mm, which are typically encountered in microtensile testing of free standing thin films and foils, micro-beam bending, and ultramicro-indentation. The machine is based on the use of compound flexures (in an integrated frame) as precision guides for actuation and as linear springs for force measurement. Results are presented from tests in different regimes of the machine’s force and displacement ranges to demonstrate its capabilities. The tests include (a) micro-tensile tests on free-standing gold thin films, rolled copper foils and elastomeric fibers, and (b) micro-indentation tests on aluminum samples. The machine yields consistent high quality data at a very high resolution.
Piezoelectric Bimorph Microphone With Serial Electrical Connection
Authors: Yi Seung Hwan , Kim Eun Sok
Published: November 2021

This paper describes a piezoelectric bimorph microphone built on Parylene-D diaphragm with two ZnO films of opposite c-axis orientations. The highest sensitivity of fabricated microphone is about 74.22 μV/μbar with proper serial electrical connections, which is about twice higher than that of individual segmented electrode. The piezoelectric bimorph microphone is very attractive since it can be fabricated low temperature under 250 °C except the first low stress nitride deposition.
Surface Micro-Machined Mirrors Using Simple Floating and Fixed Hinge Designs for Three-Layer Process
Authors: Mahatvaraj Alpha , Vora Nirav D. , Bush Jimmy , Cunningham Glenn , Biernacki Joseph J. , Frolik Jeffrey
Published: November 2021

Micro-mirrors and other hinged microstructures have numerous MEMS applications. Such micro-mirrors can be used in laser-interferometry, laser beam modulation, fiber-optical switching, laser scanners and printers and a variety of other optical applications.

A pop-up mirror device is proposed which consist of a hinged polysilicon mirror mounted on a silicon substrate. The folding mirror, with one fixed hinge and two floating hinges, is designed such that the mirror is lifted off the substrate by the linear movement of a shaft from an actuating system. The assembly uses a simple three-layer process such as MUMPS (Multi User MEMS Process). The fixed hinge is constructed in all three structural layers. The mirror lifting arm and the mirror arm are designed in both the second and the third structural layers and the floating hinge, linking them, is formed by cross members of the second and third structural layers.

The motion of the mirror for different mirror lengths was simulated. Based on these predictions the geometry of the mirror was determined and then the components were simulated for various mechanical loads. The initial simulations of the device involved analyzing the stresses and displacements of the mirror and the mirror lift arm. The stress on the components was found to be acceptable for preliminary fabrication prototyping.
The Knudsen Compressor As an Energy Efficient Micro-Scale Vacuum Pump
Authors: Young M. , Vargo S. , Shiflett G. , Muntz E. P. , Green Amanda
Published: November 2021

The low-pressure pumping limit of the MEMS Knudsen Compressor, a thermal transpiration pump, is identified and discussed. The practical low-pressure limit is due to a requirement for an approach to continuum flow in the connector section, it is roughly 10mTorr. A previously developed transitional flow model was used to size several Knudsen Compressor cascades that operate down to the low-pressure limit. Designs based on previous experimental Knudsen Compressors do not provide the necessary pumping efficiency. A design, employing carefully sized capillaries etched in aerogel transpiration membranes, is shown to result in a viable device. A cascade incorporating this design provides a gas flow rate of 3E16 mol/sec, while pumping from a pressure of 10mTorr to 1 atm. It requires a volume of 73 cm3 and 2.0 W. Design considerations are outlined for MEMS Knudsen Compressors operating at their lower pressure limit. A primary concern, efficiently transitioning from the capillary section to the connector at constant temperature is discussed.
The Fabrication and Test of a Phase-Change Micropump
Authors: Yoon Hyeun Joong , Sim Woo Young , Yang Sang Sik
Published: November 2021

This paper presents the fabrication and test of a phase-change type micropump with two aluminum flap valves. This micropump consists of a pair of Al flap valves and a phase-change type actuator. The actuator is composed of a heater, a silicone rubber diaphragm and a working fluid chamber. The diaphragm is actuated by the vaporization and the condensation of the working fluid. The micropump is fabricated by the anisotropic etching, the boron diffusion and the metal evaporation. The dimension of the micropump is 8.5 mm × 5 mm × 1.7 mm. The forward and the backward flow characteristics of the flap valve illustrate the appropriateness as a check valve. Also, the flow rate of the micropump is measured. When the square wave input voltage of 10 V is applied to the heater, the maximum flow rate of the micropump is 6.1 μl/min at 0.5 Hz and the duty ratio of 60% for zero pressure difference.