A Robust Lateral Shift Free (LSF) Electrothermal Micromirror With Flexible Multi-Morph Beams

Electrothermal bimorph-based scanning micromirrors typically employ widely-used silicon dioxide (SiO 2 ) as the electrical and thermal isolation material. However, due to the brittle nature of SiO 2 , such micromirrors may not be able to even survive a slight collision, which greatly limits their application range. To improve the robustness of electrothermal micromirrors, a polymer material is incorporated to partially replace SiO 2 as the electrical and thermal isolation material as well as the anchor material. In particular, photosensitive polyimide (PSPI) is used to simplify the fabrication process. In this work, PSPI-based electrothermal micromirrors have been designed, fabricated and tested. The PSPI-type micromirrors achieved a maximum optical scan angle of ± 19.6 ° and a maximum vertical displacement of 370 µm both at only 4 Vdc. With a mirror aperture size of 1mm × 1 mm, the PSPI-type micromirrors withstood over 200 g accelerations from either vertical or lateral directions in the impact experiment. In the drop test, the PSPI-type micromirrors survived falls to a hard floor at heights up to 21 cm. In the standard frequency sweeping vibration test, the PSPI-type micromirrors withstood 21 g and 29 g acceleration in the vertical and lateral vibration, respectively. In all these experimental tests, the PSPI-type micromirrors demonstrated at least 4 times better robustness compared to the SiO 2 -type micromirrors fabricated in the same batch.