ACTUATION ENHANCEMENT OF A MICRO BIMORPH THERMAL ACTUATOR
Farid Ullah Khan*
ABSTRACT
A bimorph thermal actuator (BTA) is typically used to actuate other MEMS structures, such as, micro-mirrors, atomic force microscope probe tips, membranes of micro pumps and micro valves, etc. This research is focused on enhancing BTA actuation characteristics. The mathematical model for BTA is used to study the behaviour of a spectrum of material combinations. Although a silicon-aluminum (SiO2-Al) BTA exhibits superior characteristics over a limited operational range, it is found that a silicon-stainless steel (Si-SS) bimorph provides larger deflections at higher operational conditions. The practical constraints on traditional bimorph materials in extreme operating conditions arise from intrinsic material properties such as yield strength and melting temperature. Under such extreme conditions Si-SS bimorphs perform well, opening up new field applications for this micro device. In order to fabricate the novel Si-Steel bimorph, a generic fabrication sequence is described according to criteria of reproducibility, batch fabrication, applicability and cost effectiveness with the use of newer micro fabrication techniques such Pulsed Laser Deposition (PLD), Laser Ablation (LA) and Micro electro-discharge machining (μEDM). Different designs of bimorph thermally actuated digital micro-mirror devices (DMDs) are also fabricated by the same generic fabrication process in order to show the practical utility of this research in the field of MEMS. The DMDs actuated by BTAs, are easy to fabricate and can scan through larger angles as compared to electrostatically actuated DMDs.
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December 2014
Vol 33 No 2 (2014)
