Due to the limitations of electrostatic RF actuators, magnetic actuation was investigated, and the optimal design space for a bistable magnetic actuator with ultra-low actuation energy and large actuation distance (100 m) has been modeled. Attention was paid to minimizing the energy expended to minimize heat dissipation and power consumption so that the device could be used over a wide temperature range, including cryogenic environments. A more desirable switching regime existing for low magnetic fields (10 mT) was found that requires shorter pulses (s vs ms) and lower actuation energy (less than 5 J vs 100 J) than designs outside of this space. The device was modeled to latch in two states, based on the interaction of the magnetic actuator with an external magnetic field. Based on this model, a bistable magnetic MEMS actuator was fabricated using microelectronic processes including a two-substrate flip-chip assembly, multilevel metallization, and sublimation release to avoid stiction. The actuator was found to have excellent correspondence between observed and modeled behavior. The benefits of shape anisotropy are quantified. Lithographic patterning of the magnetic material into long narrow strips along the actuators length resulted in much greater magnetic torques being developed at reduced external field levels. Low levels of anisotropy led to designs with low levels of magnetization and therefore required higher external magnetic fields, whereas high levels of anisotropy led to designs latching at 10 mT levels with contact forces greater than 5 N with switching energies less than 100 J and a switching speed of less than 5 ms. More moderate levels of anisotropy resulted in a design space where less than 1 J switching energies could be realized. Electrical performance has been demonstrated over 2 million cycles, and mechanical performance to 150 million cycles. Applications include electronics, microfluidics, and cryogenic devices.

Highly sensitive optical displacement detection methods implemented in a small volume and with reduced power consumption have a potential to compete with commonly used capacitance based methods in micromechanical sensor systems. This dissertation presents the design, implementation, and characterization of a miniaturized optomechanical displacement sensor system heterogeneously integrated with a coherent laser source and optoelectronic readout as a step in realizing this potential. The sensor uses a phase-sensitive diffraction grating built on a transparent substrate to achieve interferometric sensitivity in a small volume. The device sensitivity is actively optimized via the built-in electrostatic actuation capability, which may be utilized for self calibration and force feedback operation. Optical interconnect through the backside of the sensor enables compact integration with optoelectronic components. For optical readout, a custom-designed silicon photodiode array has been fabricated including deep reactive ion etching of through-wafer holes. The hybrid-integrated system has been implemented and characterized in an acoustic sensor application using both continuous wave and pulsed lasers to show reduced power consumption potential. Comprehensive diffraction analysis has been carried out for optical design of the integrated sensor. Furthermore, a fully-vectorial method has been formulated for general multilayered grating structures and compared with the scalar diffraction approach to investigate the effects of polarization and grating periods. In addition, a grating-assisted resonant-cavity-enhanced (GARCE) detection method has been proposed to improve the displacement sensitivity in optomechanical microsensors. Fabrication of the GARCE structures based on both metallic and dielectric mirrors has been successfully demonstrated, and preliminary experimental results have shown a good agreement with theoretical predictions. The concepts developed and demonstrated in this thesis form a technology platform which already had an impact in a variety of applications including optical microphones, micromachined ultrasonic transducers and transducers arrays, micromachined inertial sensors, and scanning probe microscopy.

Controlling tribological interactions, such as friction and adhesion between contacting interfaces is critical for the advancement of technologies such as microelectromechanical systems (MEMS) devices. The challenge in MEMS device lubrication lies in the inherent nature of the material’s surface at the nanoscale as well as the nature of the surfaces typically used during experimentation. Device surfaces often display nanoscale roughness with surface asperities dictating the tribological properties between interfaces, yet the vast majority of past research has focused predominately on nanotribological studies of thin films on flat silicon substrates to model the behavior of these self-assembled wear-reducing coatings. New model surfaces have been manufactured and integrated into experiments in which surfaces with controlled asperity sizes act as more realistic models of MEMS surfaces. As friction and adhesion between real surfaces in sliding contact are dominated by the interactions of nanoscaled surface asperities, this research is an extension of previous work, moving beyond smooth surfaces by manufacturing and implementing new experimental platforms possessing controlled asperity sizes. The influence of asperity size on the tribological properties of these contacts is being studied for both native oxide and organosilane derivatized surfaces. These studies more readily mimic the conditions found at true asperity-asperity contacts. This research has aimed to develop new lubricant thin films that can effectively protect MEMS device surfaces during use with the long term goal of bringing MEMS devices out of the laboratory and into wide scale commercial use. This work investigates how self-assembled monolayers (SAMs) on curved surfaces can be utilized in manners that their analogs on flat surfaces cannot. SAMs on curved asperities can be used to trap short chain alcohols, which during contact may be released to function as an additional lubricant layer on the surface. Both atomic force microscopy and Fourier transform infrared spectroscopy have been employed to evaluate how chain disorder influences the protective function of these molecular lubricant layers on asperities. It was found that functionalized surfaces resisted wear and were able to operate under continuous scanning for longer time frames than unfunctionalized surfaces and that multicomponent films improved upon the performance of their base, single component analogs.

Today¡¦s electronic components draw high levels of power and run at high temperature, which can present overheating problems for engineers and designers. They must find ways to keep the equipment cool or watch them fail prematurely. The conventional thermoelectric devices are high power consµming and slow response. We need more integrated and high performance thermoelectric device. Because of the limit of material characteristics, the figure of art rising with the quality of epitaxial layer. We gave a cheaper and easier fabrication to realized this demand. We present a micro thermoelectric device fabricated by Bi2Te3 electrochemical process. By using rotary cathode electrode, the current density can be well-proportioned. The thermal conduction and resistivity can be optimizing by this design. Also using the MEMS technology with repeated exposure and development of multiple photoresist layers, several different metals (Au, Cr) and thermoelectric materials (Bi2Te3, Sb2Te3) are fabricated. The SiO2 of 0.5µm was grown. Then the 0.3£gm-thick Au on oxidized Si sputtered with a 1£gm thick layer of Cr. And the bottom electrode was patterned by lift-off. Thick positive photoresist with one set of holes developed. Bi2Te3 was deposited by electrochemical deposition. And the Sb2Te3 is growing with the same method. The upper electrode sputtered with thin Au film and pattern by lift-off. Finally, Cr was etched to electrically isolate the bottom interconnects. The area of Bi2Te3 is about 50x50£gm2. And it¡¦s high about 5£gm. The ZT value of Bi2Te3, which is measured and verified to be around 0.0088.

Presently, the two-dimensional optical switch is widely applied in the field of the optics communication. Due to the restrictions of the Surface Micro-Machining in MEMS (Micro Electric-Mechanical System), the traditional optical switch can only deliver the signal of fibers in a two-dimensional plane. The common frameworks and principles of two-dimensional optical switch, array of optical switches and micro-actuators are developed. Take the advantage of developed technologies and the concept of the spatial mechanisms, a three-dimensional optical switch possessing two degree of freedoms is designed in this study. Different from the single selectivity of the signal transmission delivered by the two-dimensional optical switch, the three-dimensional optical switch designed in this study possesses two main functions of signal transmission in vertical and horizontal directions. By means of function of these two transmission directions, the signal of fibers of two different silicon substrates can be easily connected. It is believed that, the possibility and the selectivity of the signal transmission of fibers are increased.

The possibility of using residual stresses favorably as a means of self-assembling MEMS during material deposition is experimentally investigated. Two atomic force microscope cantilevers are placed in contact at their free ends. Material is isothermally electroplated onto one (the deposition) cantilever, but no material is deposited onto the other (spring) cantilever. The deposited layer contains residual stresses that deform the deposition cantilever. The deposition cantilever in turn deforms the spring cantilever, thereby doing work in the spring cantilever and proving that the two structures can selfassemble during deposition processing. An insoluble nickel electroplating process and an all-sulfate nickel solution are used for the deposition. The deflection of the selfassembled cantilevers is measured in-situ as a function of the deposited thin film thickness through the optical method of atomic force microscopy. The experimental results are compared to an analytical model which consists of Euler-Bernoulli beam theory that is modified to account for moving boundaries as the material is deposited. The model accounts for the through-thickness variation of the intrinsic strain during the electroplating. Closed-form solutions are not possible, but numerical solutions are plotted for the cantilever deflection and work on the spring cantilever as functions of the deposition thickness.

This dissertation proposes a novel packaging methodology for micro-electro-mechanical systems (MEMS) based pressure sensors by using a patterned ultra-thick (150

This work presents the fabrication, modeling, and characterization of two first-generation acoustic in-plane pressure gradient sensors. The first is a micromachined piezoelectric microphone. The microphone structure consists of a semi-rigid beam structure that rotates about torsional pivots in response to in-plane pressure gradients across the length of the beam. The rotation of the beam structure is transduced by piezoelectric cantilevers, which deflect when the beam structure rotates. Sensors with both 10 and 20-μm-thick beam structures are presented. An analytical model and multi-mode, multi-port network model utilizing finite-element analysis for parameter extraction are presented and compared to acoustic sensitivity measurements. Directivity measurements are interpreted in terms of the multi-mode model. A noise model for the sensor and readout electronics is presented and compared to measurements. The second sensor is a capacitive sensor which is comprised of two vacuum-sealed, pistons coupled to each other by a pivoting beam. The use of a pivoting beam can, in principle, enable high rotational compliance to in-plane small-signal acoustic pressure gradients, while resisting piston collapse against large background atmospheric pressure. A design path towards vacuum-sealed, surface micromachined broadband microphones is a motivation to explore the sensor concept. Fabrication of surface micromachined prototypes is presented, followed by finite element modeling and experimental confirmation of successful vacuum-sealing. Dynamic frequency response measurements are obtained using broadband electrostatic actuation and confirm a first fundamental rocking mode near 250 kHz. Successful reception of airborne ultrasound in air at 130 kHz is also demonstrated, and followed by a discussion of design paths toward improve signal-to-noise ratio beyond that of the initial prototypes presented. A method of localizing sound sources is demonstrated using the piezoelectric sensor. The localization method utilizes the multiple-port nature of the sensor to simultaneously extract the pressure gradient and pressure magnitude components of the incoming acoustic signal. An algorithm for calculating the sound source location from the pressure gradient and pressure magnitude measurement is developed. The method is verified by acoustic measurements performed at 2 kHz. / text

Advances in millimeter-scale fabrication processes have enabled rapid progress towards the development of flapping wing micro air vehicles with wing spans of several centimeters and a system mass on the order of 100mg. Concerning flight stability and control mechanisms for these mass and power limited devices, this dissertation explores the use of underactuated “mechanically intelligent” systems to passively regulate forces and torques encountered during flight. Several experiments demonstrate passive torque regulation in physical flapping wing systems. Finally, this dissertation concludes with a detailed description of the Printed Circuit MEMS manufacturing process, developed to address the practical problem of building complex insect-scale machines. / Engineering and Applied Sciences

MEMS Accelerometers are broadly used in the area of vibration sensor. Their applications range from seismic disturbances, to automotive industry such as airbag systems, active suspension, and smart braking. Traditionally, the acceleration is detected electrically by measuring either capacitive variations or piezoelectric signals. Those approaches suffer from a number of drawbacks, such as low sensitivity due to low signal-to-noise ratio (SNR), small dynamic range, high temperature sensitivity, etc. In this thesis, a MEMS-based optical accelerometer is designed and analyzed. The device can be fabricated on a silicon-on-insulator (SOI) wafer, on which a double-leg single-mode optical rib waveguide is used to propagate 1.55μm laser beam. The device integrates the waveguide with a mechanical oscillator, and is able to detect in-plane vibrations of the oscillator by taking advantages of optical interference. According to the analysis, the maximum working range of the oscillator can be as large as 50μm and the acceleration sensitivity can be below 1μg/Hz¹/². Device fabrication and characterization are also carried out and described in the thesis. All necessary fabrication steps and details as well as characterization setups are given. Due to several fabrication challenges in UBC (e.g. malfunctioned equipment), a complete device has not been fabricated. More fabrication and characterizations are to be continued as future work.