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 turn vertical displacement is measured at only 5.3 V for a fabricated 0.8 turn by 0.8 mm micromirror, and both the lateral shift (10 mu m) and tilting angle (0.7 degrees) 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. (c) 2007 Elsevier B.V. All rights reserved.