Programming Vanadium Dioxide Based MEMS Mirror

The programming of different mechanical states of the tip-tilt piston vanadium dioxide (VO2)-based MEMS micromirror is presented. VO2 is a smart material that exhibits a solid-to-solid phase change transition at around 68 °C which spans about 10 °C. During the transition the mechanical properties of the material change, inducing a stress on the microstructure generating a displacement. The micromirror device has a fill-factor of 32.8% and is actuated through Joule heating, using monolithically integrated resistive heaters. The hysteretic behavior of the VO2 is exploited to program either rotational angles (tilt-mode) or vertical displacements (piston-mode) of the device. The tilt-mode is divided in two components: pitch and roll. The programming of each mode is realized by applying a constant current to pre-heat the VO2 film within the transition temperature and adding electrical pulses to move between states. The maximum power consumed when programming the two states is measured for each actuation mode. The repeatability of the programming actions is demonstrated by showing an identical sequence of programming pulses produced the same mechanical state for the rotational angle (tilt-mode) and vertical displacement (piston-mode). Finally, it is demonstrated that different states can be programmed by using the same pre-heating temperature and programming pulses at different magnitudes.