As technology advances and engineering capabilities improve, more research has focused on microscopic possibilities. Microelectromechanical systems (MEMS) is one area that has received much attention recently. Within MEMS much research has focused on sensing and actuation. This thesis presents work on a particular actuator of interest, the thermomechanical in-plane microactuator (TIM). Recent work has shown the possibility of a novel approach of sensing mechanical outputs of the TIM without ancillary sensors. This sensing approach exploits the piezoresistive property of silicon. However, to implement this approach a full model of the TIM would need to be obtained to describe the physics of the TIM, as well as development of a calibration approach to account for variations between devices. This thesis develops a multi-physics model of the TIM to realize this sensing approach. This model determines the mechanical state of the TIM using the same electrical signal that actuates the TIM. In this way the TIM is able to operate as a self-sensing actuator. To allow this multi-physics model to be tractable, work was done to simplify the thermal modeling of the TIM. A preliminary calibration approach was developed to adequately compensate for variations between devices. Thermal modeling and calibration were coupled with mechanical modeling and a developed sensing approach to form the full multi-physics model of the TIM. Validation testing of the model was performed with a modified calibration approach which showed good correlation with experimental data.

This work presents the modeling, design, and testing of an underwater microactuation system. It is composed of several thermomechanical in-plane microactuators (TIM) integrated with a ratchet system to provide long displacements and high forces to underwater microelectromechanical systems (MEMS). It is capable of actuating a 200µN load 110µm. It is a two-layer silicon MEMS device fabricated with a MEMS fabrication process, PolyMUMPS. This work also shows the development of an elliptic integral model to analyze the compliant fixed-guided beams in the TIM and gives new insight into the buckling behavior, reaction forces, and displacement of the beams. The derivation, verification, and practical use of the model are shown in detail. It compares the reaction force predictions from the elliptic integral model with finite element modeling results over a wide range of non-dimensional displacements and slenderness ratios. The elliptic integral model was used to design a TIM that can operate in an aqueous environment. It was designed to achieve 9µm of displacement to drive a linear ratcheting mechanism. The thermal analysis was done in ANSYS using a 3D conduction model to predict the temperature of the heated beams. The TIM was designed to operate with a peak beam temperature of 100 ° C to prevent damage to the device due to vapor bubble formation. The main actuator showed significant electrolysis due to the high voltages used to drive the system, but otherwise functioned as predicted. Through the development and testing of the actuation system, quantitative voltage limits were discovered for underwater actuation systems under which electrolysis and boiling can be eliminated using alternating current.

This thesis introduces two ortho-planar MEMS devices that can be used to position microcomponents: the XZ Micropositioning Mechanism and the XYZ Micromanipulator. The displacement and force relationships are presented. The devices were fabricated using surface micromachining processes and the resulting mechanisms were tested. A compliant XYZ Micromanipulator was also designed to reduce backlash and binding. In addition, several other MEMS positioners were fabricated and tested: the Micropositioning Platform Mechanism (MPM), the Ortho-planar Twisting Micromechanism (OTM), and the Ortho-planar Spring Micromechanism (OSM).