Design, fabrication and control of hybrid thermal/piezoelectric MEMS array

This dissertation describes the development of a hybrid actuation solution, which utilizes a micro-machined actuator array to provide switching of mechanical motion of a larger meso-scale piezo-electric actuator. The hybrid actuator approach alleviates the main shortcoming of the conventional micro-electro-mechanical systems (MEMS)---the limited stroke and force characteristics, and combines the high-density and batch processing of the MEMS components with the high force/stroke and efficiency of the macro-scale actuation. One motivating application of this technology is the development of a portable tactile display, where discrete mechanical actuators apply vibratory excitation on the skin. The tactile display consists of three major parts: (i) MEMS 4 x 5 actuator array of individual vibrating pixels, (ii) Macro-scale piezoelectic-actuator and mechanical assembly and (iii) Control electronics module. The MEMS chip is an array of micro folded beam thermal actuators used to redirect the displacement of the main piezoelectric actuator. The electronics module includes a microcontroller and specialized drivers to control the MEMS array and the piezoelectric actuator simultaneously, generating complex pixel sequences.; Optimization of the MEMS actuator performance required in-depth understanding of the underlying actuation principles, leading to the development of a set of analytical tools for steady state and transient analysis of the microactuators. Special attention was paid to improving the commonly used linear mechanical models, which do not produce accurate results for large actuator displacements. The developed analytical models were compared against finite element simulations and showed very good agreement.; Another major contribution of this dissertation is the integration of micro fabrication, mechanical design and advanced embedded system design into a single device. This integration allowed significant decrease in size compared to the existing tactile displays. The developed prototype is completely self-contained, powered by one watch battery and approximately the size of a wristwatch. Despite its size, the device is 'intelligent' due to the use of onboard high performance microcontroller. The achieved reduction of size and power consumption is a very important step toward mainstream adoption of devices for tactile communication.