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Full-Text Articles in Mechanical Engineering
Piezoresistive Sensing Of Bistable Micro Mechansim State, Jeffrey K. Anderson
Piezoresistive Sensing Of Bistable Micro Mechansim State, Jeffrey K. Anderson
Theses and Dissertations
The objective of this work is to demonstrate the feasibility of on-chip sensing of bistable mechanism state using the piezoresistive properties of polysilicon, thus eliminating the need for electrical contacts. Changes in position are detected by observing changes in resistance across the mechanism. Sensing the state of bistable mechanisms is critical in their various applications. The research in this thesis advances the modeling techniques of MEMS devices which use piezoresistivity for position sensing. A fully compliant bistable micro mechanism was designed, fabricated, and tested to demonstrate the feasibility of this sensing technique. Testing results from two fabrication processes, Fairchild's SUMMiT …
Ortho-Planar Mechanisms For Microelectromechanical Systems, Craig P. Lusk
Ortho-Planar Mechanisms For Microelectromechanical Systems, Craig P. Lusk
Theses and Dissertations
A method for representing the design space of ortho-planar mechanisms has been developed. The method is based on the Theorem of Equality of Orientation Set Measures (TEOSM) which allows mechanisms to be represented by points in an abstract space. The method is first developed for single loop planar folded mechanisms with revolute joints, and later extended to mechanisms with prismatic joints and to spherical folded mechanisms. Functions which assign a value to each point in design space can be used to describe classes of mechanisms and evaluate their utility for MEMS design. Additionally, this work introduces the use of spherical …
Design And Development Of A Mems-Based Capacitive Bending Strain Sensor And A Biocompatible Housing For A Telemetric Strain Monitoring System., Julia Marie Weyer Aebersold 1969-
Design And Development Of A Mems-Based Capacitive Bending Strain Sensor And A Biocompatible Housing For A Telemetric Strain Monitoring System., Julia Marie Weyer Aebersold 1969-
Electronic Theses and Dissertations
Lumbar arthrodesis or spinal fusion is usually performed to relieve back pain and regain functionality from ruptured discs, disc degenerative disease, trauma and scoliosis. Metal rods are often fixed to the spine with screws or hooks, while fusion develops on the affected vertebrae. Fusion is determined by visual examination of radiographic images (X-ray), computed tomography (CT) scans or magnetic resonance imaging (MRI), yet these inspection procedures are subjective methods of review. They do not objectively confirm the presence of spinal fusion, which can lead to exploratory surgery to determine if fusion has occurred. Therefore, a need has arisen to develop …
Electrothermomechanical Modeling Of A Surface-Micromachined Linear Displacement Microactuator, Christian D. Lott
Electrothermomechanical Modeling Of A Surface-Micromachined Linear Displacement Microactuator, Christian D. Lott
Theses and Dissertations
The electrothermomechanical characteristics of an electrically-heated polycrystallinesilicon microactuator are explored. Using finite-difference techniques, an electrothermal model based on the balance of heat dissipation and heat losses is developed. For accurate simulation, the relevant temperature dependent properties from the microactuator material are included in the model. The electrothermal model accurately predicts the steady-state power required to hold position, and the energy consumed during the thermal transient. Thermomechanical models use the predictions of temperature from the electrothermal solution to calculate displacement and force from pseudo-rigid-body approximations and commercial finite-element code. The models are verified by comparing experimental data to simulation results of …
Dual-Stage Thermally Actuated Surface-Micromachined Nanopositioners, Neal B. Hubbard
Dual-Stage Thermally Actuated Surface-Micromachined Nanopositioners, Neal B. Hubbard
Theses and Dissertations
Nanopositioners have been developed with electrostatic, piezoelectric, magnetic, thermal, and electrochemical actuators. They move with as many as six degrees of freedom; some are composed of multiple stages that stack together. Both macro-scale and micro-scale nanopositioners have been fabricated. A summary of recent research in micropositioning and nanopositioning is presented to set the background for this work. This research project demonstrates that a dual-stage nanopositioner can be created with microelectromechanical systems technology such that the two stages are integrated on a single silicon chip. A nanopositioner is presented that has two stages, one for coarse motion and one for fine …
Simulation-Based Design Under Uncertainty For Compliant Microelectromechanical Systems, Jonathan W. Wittwer
Simulation-Based Design Under Uncertainty For Compliant Microelectromechanical Systems, Jonathan W. Wittwer
Theses and Dissertations
The high cost of experimentation and product development in the field of microelectromechanical systems (MEMS) has led to a greater emphasis on simulation-based design for increasing first-pass design success and reliability. The use of compliant or flexible mechanisms can help eliminate friction, wear, and backlash, but compliant MEMS are sensitive to variations in material properties and geometry. This dissertation proposes approaches for design stage uncertainty analysis, model validation, and robust optimization of nonlinear compliant MEMS to account for critical process uncertainties including residual stress, layer thicknesses, edge bias, and material stiffness. Methods for simulating and mitigating the effects of non-idealities …
Non-Silicon Microfabricated Nanostructured Chemical Sensors For Electric Nose Application, Jianwei Gong
Non-Silicon Microfabricated Nanostructured Chemical Sensors For Electric Nose Application, Jianwei Gong
Electronic Theses and Dissertations
A systematic investigation has been performed for "Electric Nose", a system that can identify gas samples and detect their concentrations by combining sensor array and data processing technologies. Non-silicon based microfabricatition has been developed for micro-electro-mechanical-system (MEMS) based gas sensors. Novel sensors have been designed, fabricated and tested. Nanocrystalline semiconductor metal oxide (SMO) materials include SnO2, WO3 and In2O3 have been studied for gas sensing applications. Different doping material such as copper, silver, platinum and indium are studied in order to achieve better selectivity for different targeting toxic gases including hydrogen, carbon monoxide, hydrogen sulfide etc. Fundamental issues like sensitivity, …
Uv-Liga Compatible Electroformed Nano-Structured Materials For Micro Mechanical Systems, Bo Li
Uv-Liga Compatible Electroformed Nano-Structured Materials For Micro Mechanical Systems, Bo Li
Electronic Theses and Dissertations
UV-LIGA is a microfabrication process realzed by material deposition through microfabricated molds. UV photolithography is conducted to pattern precise thick micro molds using UV light sensitive materials, mostly SU-8, and electroforming is performed to fabricate micro metallic structures defined by the micro molds. Therefore, UV-LIGA is a bottom-up in situ material-addition process. UV-LIGA has received broad attention recently than LIGA a micro molding fabrication process using X-ray to pattern the micro molds. LIGA is an expansive and is limited in access. In comparing to LIGA, the UV-LIGA is a cost effective process, and is widely accessible and safe. Therefore, …
Simulations And Experimental Analysis Of High-Aspect-Ratio Diffusive Micro-Mixers, Amit Maha
Simulations And Experimental Analysis Of High-Aspect-Ratio Diffusive Micro-Mixers, Amit Maha
LSU Master's Theses
Passive (diffusional) mixing has been used in designing high-aspect-ratio micro-mixers for the purpose of performing the Liagase Detection Reaction (LDR). A simple model was used to design such mixers optimized for pressure drop or time required to deliver a prescribed volume of mixture. The types of mixers considered are simple, cheap, and durable and can perform over a broad range of volumetric flow rates at reasonably modest pressure drops. The fluids typically have a very low diffusion coefficient of=1.2x10^10m^2/s, and thus diffusional mixing can only be effective in high-aspect-ratio micro-channels. A realizable aspect ratio of 6 has been considered initially …