Sakshi Pathneja Int. Journal of Engineering Research and Applications www.ijera.com ISSN : 2248-9622, Vol. 4, Issue 7( Version 5), July 2014, pp.34-37 www.ijera.com 34 | Page Analysis and Optimization of an Electro-Thermally and Laterally Driven Poly-Silicon Micro-Actuator Sakshi Pathneja , P. Raja (ECE Department, BRCM College of Engineering & Technology, BAHAL, BHIWANI, India) ABSTRACT A Large displacement at low voltage is generally provided by electro-thermal mechanisms. A 3-D MEMS electro-thermal micro-actuator has been designed and simulated using COMSOL Multiphysics 4.3 which is geometrically optimized to explore the effect of dimensional variation on its performance. Metallic electro- thermal actuators provide large displacements at low voltages but at the same time, the maximum temperature in the device rises very sharply due to their highly conductive nature. To overcome this problem, a semi-conductor material; poly-silicon which is compatible with IC technology is used. For further improvements in terms of displacement and temperature, the geometry of the actuator is optimized. Keywords: MEMS, Electro-thermal Actuator, Joule Heat, Thermal Expansion. I. INTRODUCTION Micro-robotics, micro-surgery, micro-fluidics, micro-relays, assembling and miniature medical instrumentation, microgrippers find applications in almost every field. There may be different actuation principles involved like electro-thermal, electrostatic, piezoelectric, shape memory and electromagnetic. Out of which thermal actuation is the most accurate. Actuators based on principle of electrothermal actuation are most widely used in MEMS. The most well known type of thermally actuated compliant mechanisms is the so-called “electrothermal- compliant” (ETC) micro-actuators. Micro-gripper is comprised of two micro-actuators (hot-and-cold- arm actuator) which operates on the basis of thermal expansion generated by non-uniform joule heating. Non-uniform heat may be produced either by using different materials with different coefficient of thermal expansion (CTE) or by using two beams of same material but different cross-sections. Micro- actuator consists of two arms one of which is the narrower cold arm and the wider hot arm. The wider arm is joined to the anchor with the help of flexure joints as shown in figure 1. When voltage is applied in series to this structure, the Current will flow through these arms with same heat distribution. Thus the narrower arm gets more heated due to small resistance according to the relations; R= ρ L /A and H=I2 R, where R is the resistance, L is the length and A is the area of cross section of the arm, H is the Joule heat produced in the arm and I is the current flowing through the arm. So the narrower arm gets more heated and it will deflect more than the wider arm. If voltage is applied in the opposite direction the structure stretches in the parallel direction. Figure 1: (a) Series Arrangement (b) Parallel Arrangement in Electro-thermal Actuator II. DESIGN CONCEPT The dimensions of the structure are as follows (575μm × 175.5μm) area, including contact pads. The two arms of the actuator have same cross sectional area but different lengths. The actuator consists of the two beams, one wide (cold) and other narrow (hot) that are joined at free end. Both the beams are anchored at other end. The driving mechanism for this actuator is based on asymmetric thermal expansion due to Joule heating. The structure is made up of poly-silicon for compatibility with IC technology. The initial dimensions of the micro-actuator are as given in the table 1 and its design is shown in figure 2. RESEARCH ARTICLE OPEN ACCESS