Traumatic brain injury (TBI) affects 1.4 million people a year in the United States alone and despite the fact that 96% of people survive a TBI, the health and socioeconomic consequences can be grave, partially due to the fact that very few clinical treatments are available to reduce the damage and subsequent dysfunction following TBI. To better understand the various mechanical, electrical, and chemical events during neural injury, and to elucidate specific cellular events and mechanisms that result in cell dysfunction and death, new high-throughput models are needed to recreate the environmental conditions during injury. This thesis project focuses on the creation of a novel and clinically relevant single-cell injury model of traumatic brain injury (TBI). The implementation of the model requires the development of a novel injury device that allows specialized micro-interfacing functionality with neural micro environments, which includes the induction of prescribed strains and strain rates onto neural tissue, such as groups of cells, individual cells, and cell processes. The device consists of a high-resolution micro-electro-mechanical-system (MEMS) microtweezer microactuator tool that is introducible into both biological and aqueous environments and can be proximally positioned to specific targets in neural tissue and neural culture systems. This microtweezer, which is constructed using traditional photolithography and micromachining processes, is controllable by a custom developed software-automated controller that incorporates a high precision linear actuator and utilizes a luer-based microtool docking interface. The injury studies will include examination of intracellular calcium concentration over the injury time course to evaluate neuronal plasma membrane permeability, which is a significant contributor to secondary injury cascades following initial mechanical insult. Mechanical strain and strain rate input tolerance criteria will also be used to determined thresholds for cellular dysfunction and death.

Thesis (M.Eng.)--University of Wollongong, 2005. / Typescript. Includes bibliographical references: leaf 98-102.

Trilayer polypyrrole microactuators that can operate in air have previously been developed. They consist of two outer layers ofthe electroactive polymer polypyrrole (PPy) and one inner layer of a porous poly(vinylidene flouride) (PVDF) membranecontaining a liquid electrolyte. The two outer layers of PPy are each connected with gold electrodes and separated by the porousPVDF membrane. This microtool is fabricated by bottom-up microfabrication However, porous PVDF layer is not compatible with bottom upmicrofabrication and highly swollen SPE suffers from gold electrode delamination. Hence, in this MSc project/thesis a novelmethod of flexible electrode fabrication with conducting polymers was developed by soft lithography and drop-on-demandprinting. The gold electrodes were replaced by patterned vapor phase polymerized (VPP) poly(3,4-ethylenedioxythiophene) (PEDOT)electrodes due to its high electrical conductivity and versatile process ability. The replacement of the stiff gold electrodes byflexible and stretchable PEDOT allowed high volume change of the material and motions. The PEDOT electrodes werefabricated by patterning the oxidant iron tosylate using microcontact printing and drop-on-demand printing. Moreover, thePVDF membrane has been replaced by a nitrile butadiene rubber/poly(ethylene oxide) semi-interpenetrating polymer network(IPN) to increase ion conductivity and strechability and hence actuator performance.

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 motion; both are fabricated by surface micromachining. The nanopositioner has one translational degree of freedom. Thermal microactuators operate both stages. The first stage includes a bistable mechanism: it travels 52 micrometers between two discrete positions. The second stage is mounted on the first stage and moves continuously through an additional 8 micrometers in the same direction as the first stage. Two approaches to the control of the second stage are evaluated: first, an electrical input is transmitted to an actuator that moves with the first stage; second, a mechanical input is applied to an amplifier mechanism mounted on the first stage after completing the coarse motion. Four devices were designed and fabricated to test these approaches; the one that performed best was selected to fulfill the objective of this work. Thermal analysis of the actuators was performed with previously developed tools. Pseudo-rigid-body models and finite element models were created to analyze the mechanical behavior of the devices. The nanopositioners were surface micromachined in a two-layer polysilicon process. Experiments were performed to characterize the resolution, repeatability, hysteresis, and drift of the second stages of the nanopositioners with open-loop control. Position measurements were obtained from scanning electron micrographs by a numerical procedure, which is described in detail. The selected nanopositioner demonstrated 170-nanometer resolution and repeatability within 37 nanometers. The hysteresis of the second stage was 6% of its full range. The nanopositioner drifted 25 nanometers in the first 60 minutes of operation with a time constant of about 6 minutes. The dual-stage nanopositioner may be useful for applications such as variable optical attenuators or wavelength-specific add--drop devices.

In this work, new small deflection magnetic actuators have been proposed, designed, and tested for applications in Surface Enhanced Raman Scattering optical sensors. Despite the fact that SERS sensors have been shown to increase Raman over ten orders of magnitude for molecular detection, several technological challenges have prevented the design of practical sensors, such as making SERS sensors that can efficiently detect a wide variety of molecules. Since the optimum signal-to-noise in SERS occurs at different excitation wavelengths for different molecules, individual metal nanostructures need to be designed and fabricated for each independent chemical species. One possible solution to this problem is to tune the plasmon resonance frequency of the metal nanoparticles to eliminate the need for individually optimized particles. In order to achieve a tunable local dielectric environment, and thus allow for control over the resonance frequency of metal nanoparticles, a new SERS sensor geometry is proposed and a large deflection magnetic actuator is fabricated and tested as a starting point for the design of a small deflection magnetic actuator. Using the newly developed SERS geometry and the optimized fabrication processing techniques, two small deflection magnetic actuator beam structures were designed, fabricated, and tested. These devices utilizes an off-chip electromagnet source able to produce a magnetic force of approximately 14 μN on the on-chip nickel film generating deflections up to 139 nm for the straight beam device and 164 nm for the curved beam device. iii In the process of characterizing the newly developed small deflection magnetic actuator, an integrated magnetic actuator with electrostatic restoration geometry was conceived. This device was designed to meet the specifications of the small deflection magnetic actuator as well as eliminate the need of an off-chip magnetic source and fully integrate the process atop the metal nanoparticle arrays. Using adhesive iron based magnetic strips as the magnetic drive source, circular NiFe beams with 1, 2, 3, and 4 mm diameters were designed and simulated. Calculations predicted maximum achievable actuation of up to 2.5 μm. Processing steps were laid out for a set of integrated devices as a possible predecessor to the newly designed small deflection magnetic actuator.

The next generation of biomedical tools requires reshapeable electronics to closely interface with biological tissues. This will offer unique mechanical properties and the ability to conform to irregular geometries while being robust and lightweight. Such devices can be achieved with soft materials and thin-film structures that are able to reshape on demand. However, reshaping at the submillimeter scale remains a challenging task. Herein, shape-controlled microscale devices are demonstrated that integrate electronic sensors and electroactive polymer actuators. The fast and biocompatible actuators are capable of actively reshaping the device into flat or curved geometries. The curvature and position of the devices are monitored with strain or magnetic sensors. The sensor signals are used in a closed feedback loop to control the actuators. The devices are wafer-scale microfabricated resulting in multiple functional units capable of grasping, holding, and releasing biological tissues, as demonstrated with a neuronal bundle.

Energy efficiency is a vital key component when designing and miniaturizing self sustained microsystems. The smaller the system, the smaller is the possibility to store enough stored energy for a long and continuous operational time. To move such a system in an energy efficient way, a piezoelectrical locomotion module consisting of four resonating cantilevers has been designed, manufactured and evaluated in this work. The combination of a suitable substrate, a multilayered piezoelectric material to reduce the voltage, and a resonating drive mechanism resulted in a low power demand. A manufacturing process for multilayer cantilever actuators made of P(VDF-TrFE) with aluminum electrodes on a substrate of flexible printed circuit board (FPC), has been developed. An important step in this process was the development of an etch recipe for dry etching the multilayer actuators in an inductive plasma equipment. Formulas for the quasi static tip deflection and resonance frequency of a multilayered cantilever, have been derived. Through theses, it was found that the multilayered structures should be deposited on the polymer side of the FPC in order to maximize the tip deflection. Both a large and a miniaturized locomotion module were manufactured and connected by wires to verify that the three legged motion principal worked to move the structures forward and backward, and turn it right and left. By touching and adding load, to a fourth miniaturized cantilever, its ability to act as a contact sensor and carry object was verified. The presented locomotion module is part of a multifunctional microsystem, intended to be energy efficient and powered by a solar panel with a total volume of less than 25 mm3 and weight 65 mg. The whole system, consisting of a solar cell, an infra red communication module, an integrated circuit for control, three capacitors for power regulating, the locomotion module and an FPC connecting the different modules, was surface mounted using a state of the art industrial facility. Two fully assembled systems could be programmed both through a test connector and through optical sensors in the multifunctional solar cell. One of these was folded together to the final configuration of a robot. However, the entire system could not be tested under full autonomous operating conditions. On the other hand, using wires, the locomotion module could be operated and used to move the entire system from a peak-to-peak voltage of 3.0 V.

This research focuses on the development of polymer microfabrication technologies for the realization of two major components of a pneumatic tactile display: a microactuator array and a complementary microvalve (control) array. The concept, fabrication, and characterization of a kinematically-stabilized polymeric microbubble actuator (¡°endoskeletal microbubble actuator¡±) were presented. A systematic design and modeling procedure was carried out to generate an optimized geometry of the corrugated diaphragm to satisfy membrane deflection, force, and stability requirements set forth by the tactile display goals. A refreshable Braille cell as a tactile display prototype has been developed based on a 2x3 endoskeletal microbubble array and an array of commercial valves. The prototype can provide both a static display (which meets the displacement and force requirement of a Braille display) and vibratory tactile sensations. Along with the above capabilities, the device was designed to meet the criteria of lightness and compactness to permit portable operation. The design is scalable with respect to the number of tactile actuators while still being simple to fabricate. In order to further reduce the size and cost of the tactile display, a microvalve array can be integrated into the tactile display system to control the pneumatic fluid that actuates the microbubble actuator. A piezoelectrically-driven and hydraulically-amplified polymer microvalve has been designed, fabricated, and tested. An incompressible elastomer was used as a solid hydraulic medium to convert the small axial displacement of a piezoelectric actuator into a large valve head stroke while maintaining a large blocking force. The function of the microvalve as an on-off switch for a pneumatic microbubble tactile actuator was demonstrated. To further reduce the cost of the microvalve, a laterally-stacked multilayer PZT actuator has been fabricated using diced PZT multilayer, high aspect ratio SU-8 photolithography, and molding of electrically conductive polymer composite electrodes.

This thesis presents methods for fabricating MicroElectroMechanical System (MEMS) actuators and high-flow gas microvalves using wafer-level integration of Shape Memory Alloys (SMAs) in the form of wires and sheets. The work output per volume of SMA actuators exceeds that of other microactuation mechanisms, such as electrostatic, magnetic and piezoelectric actuation, by more than an order of magnitude, making SMA actuators highly promising for applications requiring high forces and large displacements. The use of SMAs in MEMS has so far been limited, partially due to a lack of cost efficient and reliable wafer-level integration approaches. This thesis presents new methods for wafer-level integration of nickel-titanium SMA sheets and wires. For SMA sheets, a technique for the integration of patterned SMA sheets to silicon wafers using gold-silicon eutectic bonding is demonstrated. A method for selective release of gold-silicon eutectically bonded microstructures by localized electrochemical etching, is also presented. For SMA wires, alignment and placement of NiTi wires is demonstrated forboth a manual approach, using specially built wire frame tools, and a semiautomatic approach, using a commercially available wire bonder. Methods for fixing wires to wafers using either polymers, nickel electroplating or mechanical silicon clamps are also shown. Nickel electroplating offers the most promising permanent fixing technique, since both a strong mechanical and good electrical connection to the wire is achieved during the same process step. Resistively heated microactuators are also fabricated by integrating prestrained SMA wires onto silicon cantilevers. These microactuators exhibit displacements that are among the highest yet reported. The actuators also feature a relatively low power consumption and high reliability during longterm cycling. New designs for gas microvalves are presented and valves using both SMA sheets and SMA wires for actuation are fabricated. The SMA-sheet microvalve exhibits a pneumatic performance per footprint area, three times higher than that of previous microvalves. The SMA-wire-actuated microvalve also allows control of high gas flows and in addition, offers benefits of lowvoltage actuation and low overall power consumption. / QC 20120514

The development of micro and nano-electromechanical systems (MEMS and NEMS) with entirely new or improved functionalities is typically based on novel or improved designs, materials and fabrication methods. However, today’s micro- and nano-fabrication is restrained by manufacturing paradigms that have been established by the integrated circuit (IC) industry over the past few decades. The exclusive use of IC manufacturing technologies leads to limited material choices, limited design flexibility and consequently to sub-optimal MEMS and NEMS devices. The work presented in this thesis breaks new ground with a multitude of novel approaches for the integration of non-standard materials that enable the fabrication of 3D micro and nanoelectromechanical systems. The objective of this thesis is to highlight methods that make use of non-standard materials with superior characteristics or methods that use standard materials and fabrication techniques in a novel context. The overall goal is to propose suitable and cost-efficient fabrication and integration methods, which can easily be made available to the industry. The first part of the thesis deals with the integration of bulk wire materials. A novel approach for the integration of at least partly ferromagnetic bulk wire materials has been implemented for the fabrication of high aspect ratio through silicon vias. Standard wire bonding technology, a very mature back-end technology, has been adapted for yet another through silicon via fabrication method and applications including liquid and vacuum packaging as well as microactuators based on shape memory alloy wires. As this thesis reveals, wire bonding, as a versatile and highly efficient technology, can be utilized for applications far beyond traditional interconnections in electronics packaging. The second part presents two approaches for the 3D heterogeneous integration based on layer transfer. Highly efficient monocrystalline silicon/ germanium is integrated on wafer-level for the fabrication of uncooled thermal image sensors and monolayer-graphene is integrated on chip-level for the use in diaphragm-based pressure sensors. The last part introduces a novel additive fabrication method for layer-bylayer printing of 3D silicon micro- and nano-structures. This method combines existing technologies, including focused ion beam implantation and chemical vapor deposition of silicon, in order to establish a high-resolution fabrication process that is related to popular 3D printing techniques. / <p>QC 20121207</p>