Research on characteristics of symmetric optothermal microactuators

This paper proposes and studies symmetric optothermal microactuators (OTMAs) which are directly controlled by a laser beam. Based on the principle of thermal flux, a theoretical model is established to describe the laser-induced temperature rises and optothermal expansions of the OTMAs' expansion arms. Temperature rise distributions of the arms with lengths of 590, 990, and 2260 μm are simulated separately, which reveals that, under 2 mW laser irradiation, the maximum temperature rises are invariably less than 75.9°C. Simulations are also made to consider optothermal expansions of the arms caused by laser irradiation, which turns out that expansion increases considerably when the arm's length increases from 250 to 1000 μm, while insignificantly between 1250 and 2500 μm. Under a laser beam of 2 mW power, experiments on three microfabricated OTMAs have been further conducted, which demonstrate that the OTMAs are capable of generating maximum deflections of 7.3, 11.3, and 13.6 μm, and that the growth of deflection is comparatively obvious in the case when the total length changes from 750 to 1200 μm, while insignificant for the range between 1200 and 2380 μm. With regard to simulations and experiments, it has been proved that the OTMAs are capable of implementing direct laser-controlled microactuation in which only about 2 mW laser power is demanded. Moreover, it has been proved that twofold total length or arm length does not correspondingly result in doubling the deflection, nor the expansion. Therefore, total length/expansion arm's length around or less than 1200/1000 μm is more appropriate for obtaining satisfactory characteristics of OTMAs, which may be potentially applied in MEMS/MOEMS and micro-/nano-technology.