This thesis examines the development and testing of a novel 2 DOF (Degrees of Freedom) thermal actuator using Micro Electro Mechanical Systems (MEMS) technology. A out-of-plane displacement measurement technique based on optical focus adjustments is also implemented and tested. In-plane displacement measurement techniques are also compared. Existing MEMS actuator can either move in-plane or out-of-plane but no reported actuators were found to move in a user selectable combination of both domains. The novel actuator fabricated using the PolyMUMPs process is capable of displacements of 5 ?m out-of-plane and 1.5 ?m in-plane. A Finite Element Analysis (FEA) was performed as a proof of concept prior to physical construction. FEA was also used to characterize the actuator. Measuring out-of-plane displacements of MEMS devices is difficult to accomplish using only a standard microscope and camera setup. Methods have included tilting the chip so the vertical motion has a planar component. The most common commercial measurement technique uses interferomery but special expensive equipment is necessary. A method adapted from biological autofocus is proposed in which multiple images (100+) are taken at various focal planes. An algorithm is applied which extracts the most focused image. An out-of-plane displacement measurement can be extracted between two image sets. Results were compared to optical profiler measurements and the results had an average error of 0.47 ?m A comparison of planar displacement measurement methods, which included two variations of both edge detection and pattern matching along with measurements using the optical profiler, was accomplished. Consistent planar displacement results were collected for all techniques except for the simple edge detection.

Additive manufacturing is revolutionizing the aerospace, transportation, energy, healthcare and various consumer product industries, replacing centralized manufacturing plants with more localized fabrication. 3D printing has become ubiquitous within these industries for prototyping and production. Currently, the smallest 3D printed features are on the order of a micron. While sufficient for some academic and industry applications, nanoscale features are required for the electronics industry and research endeavors. Optical lithography is still the workhorse for industrial nanofabrication utilizing large expensive commercial foundries. Here, an atomic scale 3D printer is presented with many of the features found in a complex semiconductor fabrication plant. This process is reproduced using three separate die with microelectromechanical systems (MEMS), which are bonded together to create an integrated 3D printer with the capability to print at the atomic scale. Due to the microscale size and surface areas of MEMS devices, they are extremely sensitive with rapid response times. These onboard MEMS devices replicate the functions of a thermal evaporator, patterning mask, mass sensor, heaters, temperature sensors and Van de Pauw setups. The assembled 3D printer dimensions are 3.8 mm x 2.5 mm x 1.8 mm (LxWxH) and it is therefore ideal for cryogenic environments. Quenched condensed thin film metals can be deposited using the atomic scale thermal evaporators in varying thicknesses up to approximately 50 nm. Replacing the atomic scale evaporators with microscale evaporators, the deposited film thickness can reach 3.5 microns. Evaporated films are monitored during and after the deposition with the embedded MEMS devices. While this particular 3D printing assembly is designed for research-scale investigations, the same technology could be extended to wafer-scale 3D printing with high resolution, rapid throughput, and reduced cost. / 2023-06-01T00:00:00Z

This work examined the design, fabrication, and testing of a bio-mimetic MEMS earthworm crawler with external actuators. The micro-earthworm consisted of a passive mobile shuttle with two flexible diamond shaped segments; each segment was independently squeezed by a pair of stationary chevron-shaped thermal actuators. By applying a specific sequence of squeezes to the earthworm segments, the shuttle could be driven backwards or forwards. Unlike existing inchworm drives, which use separate clamping and thrusting motors, the earthworm motor applies only clamping forces and lateral thrust is produced by the shuttle’s compliant geometry. A study of existing crawler work was performed; to the author’s knowledge, this was the first micro-crawler to achieve both clamping force and lateral motion using the same actuators. The earthworm assembly was fabricated using the POLYMUMPs process, with planar dimensions of 400 µm wide by 800 µm long. The stationary earthworm motors operated within the range of 4-9 V, and 0-10 kHz; these motors provided a maximum shuttle range of motion of 350 µm (~half the size of the device), a maximum shuttle speed of 17,000 µm /s at 10 kHz, and a maximum DC shuttle force of 80 µN. The shuttle speed was found to vary linearly with both input voltage and input frequency; the shuttle force was found to vary linearly with actuator voltage. The tested design had higher force, range, and speed (per device footprint) than most other existing designs. Future work recommendations included the implementation of multiple motors and a closed loop control system to allow an indefinite range of motion, as well as the investigation of a two degree of freedom crawler. / THE DESIGN AND TESTING OF A BIO-INSPIRED HIGH PRECISION, HIGH SPEED, LONG RANGE PERISTALTIC MICRO-MOTOR

The purpose of this thesis is to introduce a novel method of dry micro-object manipulation and to demonstrate predictable vision-based control. The Lift and slide conveyors presented utilize three main components: pads, lifters and a floating platform. The pads have a small planar displacement in the XY axis and lifters have a small Z axis displacement. Together they can be used to create minute displacements per cycle while carrying a floating platform that can hold the desired objects to be moved. These platforms can be handed off to other pad-lifter groups to create an unlimited planar envelope. Two degree of freedom control was established using LabView with open and closed loop routines. A model is presented that predicts the resonance frequencies with different loading and geometric characteristics to aid in design optimization for various applications. Parameters such as velocity, drift and traction are well characterized for different operating conditions.

This thesis presents the design and fabrication of a re-configurable micromirror array which can be used as a component of an optical microspectrometer. In an optical microspectrometer, an array of mechanically positionable micromirrors can be implemented as a reconfigurable exit slit to selectively focus particular wavelengths of a diffracted spectrum onto the detector stage. The signal to noise ratio and response time of an optical microspectrometer can be vastly improved by this technique. In the approach presented here, a hybrid bulk- and surface- micromachining process is demonstrated for fabrication of a 1XN array of micromirrors. The reconfigurable micromirrors presented here comprise of two elements, a surfacemicromachined positioning mechanism, and a bulk-micromachined mirror. These elements are finally integrated using a flip-chip bonding technique. The integrated micromirror assembly can be positioned by means of a driving mechanism consisting of arrayed electrothermal actuators. Various techniques for fabricating the micromirror array components are discussed in detail in this thesis along with a review of techniques applicable for integrating the individual components. In order to enhance the efficiency of the positioning system, the classic electrothermal actuators were redesigned in this research. The modified design of thermal actuators is introduced in this thesis. An analysis of the modified thermal actuators is also presented to demonstrate the validity of the suggested modifications.

In this thesis, microelectrode arrays of micropumps have been designed, fabricated and characterized for transporting microfluid by AC electro-osmosis (ACEO). In particular, the 3D stepped electrode design which shows superior performance to others in literature is adopted for making micropumps, and the performance of such devices has been studied and explored. A novel fabrication process has also been developed in the work, realizing 3D stepped electrodes on a flexible substrate, which is suitable for biomedical use, for example glaucoma implant. There are three major contributions to ACEO pumping in the work. First, a novel design of 3D “T-shaped” discrete electrode arrays was made using PolyMUMPs® process. The breakthrough of this work was discretizing the continuous 3D stepped electrodes which were commonly seen in the past research. The “T-shaped” electrodes did not only create ACEO flows on the top surfaces of electrodes but also along the side walls between separated electrodes. Secondly, four 3D stepped electrode arrays were designed, fabricated and tested. It was found from the experiment that PolyMUMPs® ACEO electrodes usually required a higher driving voltage than gold electrodes for operation. It was also noticed that a simulation based on the modified model taking into account the surface oxide of electrodes showed a better agreement with the experimental results. It thus demonstrated the possibility that the surface oxide of electrodes had impact on fluidic pumping. This methodology could also be applied to metal electrodes with a native oxide layer such as titanium and aluminum. Thirdly, a prototype of the ACEO pump with 3D stepped electrode arrays was first time realized on a flexible substrate using Kapton polyimide sheets and packaged with PDMS encapsulants. Comprehensive experimental testing was also conducted to evaluate the mechanical properties as well as the pumping performance. The experimental findings indicated that this fabrication process was a promising method to create flexible ACEO pumps that can be used as medical implants and wearable devices. / Thesis (Ph.D, Mechanical and Materials Engineering) -- Queen's University, 2013-05-06 10:57:48.077

Design and analysis of polysilicon and single crystal silicon gyroscopes have been carried out. Variations in suspension design have been explored. Designs that utilize in-plane and out-of-plane sensing are studied. Damping plays an important role in determining the sense response. Reduction in damping directly affects sensor performance. The various damping mechanisms that are prevalent in gyroscopes are studied. Perforations on the proof mass are observed to significantly reduce the damping in the device when operated in air. The effects of perforation geometry and density have been analyzed. The analysis results show that there is a two orders of magnitude reduction in damping of thick gyroscope structures with optimized perforation design. Equivalent circuit lumped parameter models have been developed to analyze gyroscope performance. The simulation results of these models have been compared with results obtained from SABER, a MEMS specific system level design tool from Coventor-ware. The lumped parameter models are observed to produce faster simulation results with an accuracy comparable to that of Coventorware Three gyroscopes specific to the PolyMUMPS fabrication process have been designed and their performance analyzed. Two of the designs sense motion out-of-plane and the other senses motion in-plane. Results of the simulation show that for a given damping, the gyro design with in-plane modes gives a resolution of 4◦/s. The out-of-plane gyroscopes have two variations in suspension. The hammock suspension resolves a rate of 25◦/s in a 200 Hz bandwidth while the design with folded beam suspension resolves a rate of 2◦/s in a 12 Hz bandwidth. A single crystal silicon in-plane gyroscope has been designed with vertical electrodes to sense Coriolis motion. This design gives an order of magnitude higher capacitance change for a given rotation in comparison to conventional comb-finger design. The effects of process induced residual stress on the characteristic frequencies of the polysilicon gyroscopes are also studied. The in-plane gyroscope is found to be robust to stress variations. Analysis results indicate that the tuning fork gyroscope with the hammock suspension is the most susceptible to compressive residual stress, with a significant drop in sensitivity at high stress values.

MEMS microphones have been a research topic for the last two and half decades. The state-of-the-art comprises surface mount MEMS microphones in laptops, mobile phones and tablets, etc. The popularity and the commercial success of MEMS microphones is largely due to the steep cost reduction in manufacturing afforded by the mass scale production with microfabrication technology. The current MEMS microphones are de-signed along the lines of traditional microphones that use capacitive transduction with or without permanent charge (electret type microphones use permanent charge of their sensor element). These microphones offer high sensitivity, stability and reasonably at frequency response while reducing the overall size and energy consumption by exploiting MEMS technology. Conceptually, microphones are simple transducers that use a membrane or diaphragm as a mechanical structure which deflects elastically in response to the incident acoustic pressure. This dynamic deflection is converted into an electrical signal using an appropriate transduction technique. The most popular transduction technique used for this application is capacitive, where an elastic diaphragm forms one of the two parallel plates of a capacitor, the fixed substrate or the base plate being the other one. Thus, there are basically two main elements in a microphone { the elastic membrane as a mechanical element, and the transduction technique as the electrical element. In this thesis, we propose and study novel design for both these elements. In the mechanical element, we propose a simple topological change by introducing slits in the membrane along its periphery to enhance the mechanical sensitivity. This simple change, however, has significant impact on the microphone design, performance and its eventual cost. Introduction of slits in the membrane makes the geometry of the structural element non-trivial for response analysis. We devote considerable effort in devising appropriate modeling techniques for deriving lumped parameters that are then used for simulating the system response. For transduction, we propose and study an FET (Field Effect Transistor) coupled micro-phone design where the elastic diaphragm is used as the moving (suspended) gate of an FET and the gate deflection modulated drain current is used in the subthreshold regime of operation as the output signal of the microphone. This design is explored in detail with respect to various design parameters in order to enhance the electrical sensitivity. Both proposed changes in the microphone design are motivated by the possibilities that the microfabrication technology offers. In fact, the design proposed here requires further developments in MEMS technology for reliably creating gaps of 50-100 nm between the substrate and a large 2D structure of the order of a few hundred microns in diameter. In the First part of the thesis, we present detailed simulations of acoustic and squeeze lm domain to understand the effect slits could bring upon the behaviour of the device as a microphone. Since the geometry is nontrivial, we resort to Finite element simulations using commercial packages such as COMSOL Multiphysics and ANSYS in the structural, acoustic and Fluid-structure domains to analyze the behaviour of a microphone which has top plate with nontrivial geometry. On the simulated Finite element data, we conduct low and high frequency limit analysis to extract expressions for the lumped parameters. This technique is well known in acoustics. We borrow this technique of curve Fitting from the acoustics domain and apply it in modified form into the squeeze lm domain. The dynamic behaviour of the entire device is then simulated using the extracted parameters. This helps to simulate the microphone behaviour either as a receiver or as a transmitter. The designed device is fabricated using MEMSCAP PolyMUMPS process (a foundry Polysilicon surface micromachining process). We conduct vibrometer (electrostatic ex-citation) and acoustic characterization. We also study the feasibility of a microphone with slits and the issues involved. The effect of the two dissipation modes (acoustic and squeeze lm ) are quantified with the experimentally determined quality factor. The experimentally measured values are: Resonance is 488 kHz (experimentally determined), low frequency roll-off is 796 Hz (theoretical value) and is 780 Hz as obtained by electrical characterization. The first part of this thesis focusses on developing a comprehensive understanding of the effect of slits on the performance of a MEMS microphone. The presence of slits near the circumference of the clamped plate cause reduction in its rigidity. This leads to an increase in the sensitivity of the device. Slits also cause pressure equalization between the top and bottom of the diaphragm if the incoming sound is at relatively low frequencies. At this frequency, also known as the lower cutoff frequency, the microphone's response starts dropping. The presence of slits also changes the radiation impedance of the plate as well as the squeeze lm damping below the plate. The useful bandwidth of the microphone changes as a consequence. The cavity formed between the top plate and the bottom fixed substrate increases the stiffness of the device significantly due to compression of the trapped air. This effect is more pronounced here because unlike the existing capacitive MEMS microphones, there is no backchamber in the device fabricated here. In the second part of the thesis, we present a novel subthreshold biased FET based MEMS microphone. This biasing of the transistor in the subthreshold region (also called as the OFF-region) offers higher sensitivity as compared to the above threshold region (also called as the ON-region) biasing. This is due to the exponentially varying current with change in the bias voltage in the OFF-region as compared to the quadratic variation in the ON-region. Detailed simulations are done to predict the behaviour of the device. A lumped parameter model of the mechanical domain is coupled with the drain current equations to predict the device behaviour in response to the deflection of the moving gate. From the simulations, we predict that the proposed biasing offers a device sensitive to even sub-nanometer deflection of the flexible gate. As a proof of concept, we fabricate fixed-fixed beams which utilize CMOS-MEMS fabrication. The process involves six lithography steps which involve two CMOS and the remaining MEMS fabrication. The fabricated beams are mechanically characterized for resonance. Further, we carry out electrical characterization for I-V (current-voltage) characteristics. The second part of the thesis focusses on a novel biasing method which circumvents the need of signal conditioning circuitry needed in a capacitive based transduction due to inbuilt amplification. Extensive simulations with equivalent circuit has been carried out to determine the increased sensitivity and the role of various design variables.