Artificial Damping of MEM

A. Abrol, Y. Han, Z. Zhu, J. Clark
Auburn University,
United States

Keywords: electrical damping


In this paper, we experimentally validate the artificial damping of MEMS. It is done by feeding back a force onto the proof mass through an electrostatic force feedback (EFF) circuit. The electrostatic force is proportional to, and in the opposite direction of, the velocity of the proof mass. Previously, we had proposed and simulated the use of electrostatic feedback to control the amount of effective damping [1]. There are many applications that may benefit from increased damping such as high-frequency filters, nano-positioners, increasing bandwidth, nano-lithography, or imaging with atomic force microscopy below the thermal noise limit. Prior methods to increase damping include encapsulating gas or liquids [2, 3]. However, such methods do not allow for physical contact or enable the control of damping amount. The EFF circuit utilized in this study is composed of two main parts: a velocity sensor (BJT-based Current Conveyor) and a damping force actuator (BJT-based square root circuit) that feeds back a force that is proportional to velocity. The MEMS device consists of sense and actuation comb drives attached to a proof mass that is supported by folded flexures. The amount of energy extracted from the system per cycle mimics the effect of an overdamped system. Our feedback circuit consists of off-the-self analog electronic components for damping control. In the full paper, proof of concept will be demonstrated by comparing families of frequency responses where effective damping is increased by electrostatic force feedback while the MEMS device is exposed to the atmosphere or a vacuum. Values for damping and Q will be measured by electro micro metrology (EMM). EMM is a metrology method where mechanical quantities can be accurately measured by electronic probing. [1] Clark J. V., Misiats O., Sayed S. “Electrical control of effective mass, damping, and stiffness of MEMS devices”. IEEE Sensors Journal, 2017, 17(5): 1363-1372 [3] Hirai Y., Mori R., Kikuta H., Kato N., Inoue K. and Tanaka Y., 1998 “Resonance characteristics of micro cantilever in liquid” Japan. J. Appl. Phys. 37 7064–9 [3] Kwon T. Y., Eom K., Park J. H., Yoon D. S., Kim T. S. and Lee H. L., 2007 “ In situ real-time monitoring of biomolecular interactions based on resonating microcantilevers immersed in a viscous fluid” Appl. Phys. Lett. 90 223903