Design and analysis of a twisting-type thermal actuator for micromirrors

This paper reports the design of a novel twisting-type 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 gold and silicon dioxide or nickel and silicon nitride thin films with embedded polysilicon line heaters. With a size of only 15μm in width, 1.3μm in thickness, and 100μm in length, two bimorph actuators can result in a vertical displacement of 25μm at 10 volts dc with the span of 120μm, and thus the micromirror can rotate by angles over 20°, which is a significant improvement, compared to conventional tilting-type micromirrors. This paper was recommended for publication in revised form by Associate Editor Dongsik Kim Dong Hyun Kim received his B.S. and M.S. degrees in Mechanical Engineering from Hongik University, Korea, in 2005 and 2007, respectively. Mr. Kim is currently graduate student in the department of Mechanical Engineering at Hongik University in Seoul, Korea. His research interests include micro and nanoscale heat transfer and silicon crystallization technologies for displays. Kyung Su Oh received his B.S. and M.S. degrees in Mechanical Engineering from Hongik University, Korea, in 2005 and 2007, respectively. Mr. Oh is currently a research scientist at LG Chem. Ltd. His research interests include nanoscale heat transfer, nanotubes and fuel cells and molecular simulation technology. Seungho Park received his B.S. and M.S. degrees in Mechanical Engineering from Seoul National University, Korea, in 1981 and 1983, respectively. He then received his Ph.D. degree from U.C. Berkeley, U.S.A. in 1989. Dr. Park is currently a Professor at the department of Mechanical and System Design Engineering at Hongik University in Seoul, Korea. He served as a director of general affairs of KSME. Dr. Park’s research interests include micro and nanoscale heat transfer, molecular dynamics simulation and silicon crystallization technologies for displays.