Microscopic research on the properties of optothermal microactuators with different lever ratios

This paper presents microscopic research on properties of asymmetric optothermal microactuator (OTMA) with different lever ratios. A theoretical model is established on the basis of thermal flux theorem to describe the increase in temperature induced by laser irradiation and thermal expansion of OTMAs' expansion arms. The increases in temperature of three asymmetric OTMAs with total lengths/lever ratios of 540 μm/7.2, 1,080 μm/7.2, 1,080 μm/14.4 were simulated under irradiation of 2.8 mW laser beam, which revealed that a similar increase in temperature will distribute on three expansion arms, with maximum the temperature increase of 82.73, 87.67, and 88.03°C, respectively. Due to these increases in temperature, the arms expand longitudinally and thus the OTMAs are capable of deflecting laterally with enlarged deflection amplitudes. To obtain optimized deflecting properties, three OTMAs with aforementioned lever ratios are further microfabricated and experimented using an optical microscopic observation and measuring system combined with a charge-coupled device. The experimental results show that these OTMAs can be directly actuated by laser beam and acquire maximum deflections of 6.8, 7.2, and 11.4 μm when only 2.8 mW laser power is employed. In addition, it is demonstrated that, although doubling the lever ratio of OTMA does not correspondingly generate twofold deflection, the deflection amplitude can significantly increase with the increase in the lever ratio. With their characteristic elegances, the OTMAs are expected to be practically applied in the micro-electromechanical system and the micro-opto-electromechanical system.