A large vertical displacement electrothermal bimorph microactuator with very small lateral shift

This paper reports a novel electrothermal actuator design that can generate large vertical displacements with almost no lateral shift. The lateral-shift-free (LSF) piston motion is achieved by using a unique three-bimorph actuation mechanism. Both micromirrors and microlens holders based on this new actuator design have been fabricated using a combined surface- and bulk-micromachining process. A 0.62 mm vertical displacement is measured at only 5.3 V for a fabricated 0.8 mm by 0.8 mm micromirror, and both the lateral shift (10 μm) and tilting angle (0.7°) are very small in that full vertical displacement range. The measured resonant frequency of the vertical motion mode is about 0.5 KHz. The thermal response time is about 25 ms.