Design and fabrication of twisting-type thermal actuation mechanism for micromirrors

This paper reports the design and fabrication of a novel micromirror actuation system. The actuating mechanism for driving the micromirror combines two paralleled bimorph actuators bending in opposite directions for rotational control of the micromirror. Each actuator is structured by nickel and silicon nitride thin-films. Based on thermal and structural analyses, the geometry of the actuation system is optimized to achieve larger tilting angles of micromirrors whose sizes are of the order of 100 × 100 μm2. Operation of the actuation system shows total vertical displacements about 90 μm and tilting angles about 28° for micromirrors of 150 × 150 μm2 in size at input powers about 170 mW and about 60 μm and about 20° for micromirrors of 80 × 80 μm2 in size at input powers about 60 mW, which agree well with predictions from theoretical models and simulations using a commercial code.