Electrostatic–pneumatic activation is an actuation method for shaping thin membranes for microelectromechanical and microoptoelectromechanical systems.K. J. Gabriel, O. Tabata, K. Shimaoka, S. Sugiyama, H. Fujita "Surface normal electrostatic/pneumatic actuator" Micro Electro Mechanical Systems 92 Travemunde (Germany), Feb. 1992Cleopatra Cabuz, Thomas R. Ohnstein, Michael R. Elgersma (2000), "Electrostatic/pneumatic actuator for active surfaces" US Patent No. 09/573,460 This method benefits from operation at high speed and low power consumption.Moghimi, M. J. Chattergoon, K. N. Dickensheets, D. L. “High speed focus control capability of electrostatic–pneumatic MEMS deformable mirrors” in Proc. SPIE 8977, MOEMS and Miniaturized Systems XIII, San Francisco, CA, Mar. 2014, pp. 897709, 897709-9 It can also cause large deflection on thin membranes. Electrostatic-pneumatic MEMS devices usually consist of two membranes with a sealed cavity in between. One membrane-calling actuator deflects into the cavity by electrostatic pressure to compress air and increase air pressure. Elevated pressure pushes the other membrane and causes a dome shape. With direct electrostatic actuation on the membrane, a concave shape is achieved.
This method is used in MEMS deformable mirrors to create convex and concave mirrors.Moghimi, M. J. Wilson, C. Dickensheets, D. L. “Electrostatic-pneumatic membrane mirror with positive or negative variable optical power” in Proc. SPIE 8617, MEMS Adaptive Optics VII, San Francisco, CA, Mar. 2013, pp. 861707-1, 861707-9 Electrostatic-pneumatic actuation can double maximum displacement of a thin membrane compared to only electrostatic actuated membrane.Moghimi, M. J. Wilson, C. R. Dickensheets, D. L., “Electrostatic-pneumatic MEMS deformable mirror for focus control” 2012 International Conference on Optical MEMS and Nanophotonics (OMN), Banff, Canada, August 2012, pp. 132-133.
Moreover, mechanical advantage is possible by use of electrostatic-pneumatic actuation. Since the cavity is filled with air, mechanical amplification is lower than hydraulic machinery with a non-compressible fluid. See also
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