Vertically supported two - directional comb drive ∗

Abstract A vertically supported comb drive with the feasibility of actuation in two perpendicular directions utilizing electrostatic force from interdigitated comb-shape electrodes has been demonstrated. The prototype microstructures are made of 2 μm thick polysilicon by a standard surface micromachining process. They are vertically lifted after the final sacrificial layer releasing process and are fixed on the substrate with the assistance of micro locking springs and micro hinges. The microstructures can vibrate in the directions either parallel or normal to the comb fingers, depending on the physical setups of the supporting structures and the polarity of driving electrodes. Experimentally, under 10 V dc bias voltage and 10 V ac peak-to-peak driving voltage in air, the prototype structure is found to resonate at the first fundamental mode of 6.8 kHz in the parallel direction. In the direction normal to the surface of the comb fingers, several bands of vibration movements have been observed between 500 Hz and 11.9 kHz due to the strong coupling between the two comb structures. As such, these microresonators using the vertically supported two-directional comb drive might find potential applications in the area of MEMS or MOEMS including optical systems on a chip.