DEVELOPMENT OF NOVEL 2 DOF THERMAL MICRO ACTUATORS AND A COMPARISON OF DIFFERENT DISPLACEMENT MEASUREMENT TECHNIQUES

Abstract

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.