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Large Stroke Electrostatic Comb Drive Actuators Enabled by a Novel Flexure Mechanism



Mohammad Olfatnia, Siddharth Sood, Jason J. Gorman, Shorya Awtar


This paper reports in-plane electrostatic combdrive actuators with stroke as large as 245 μm that is achieved by employing a novel Clamped Paired Double Parallelogram (C-DPDP) flexure mechanism. The C-DP-DP flexure mechanism design offers high bearing direction stiffness (Kx) while maintaining low motion direction stiffness (Ky), over a large range of motion direction displacement. The resulting high (Kx /Ky) ratio mitigates the on-set of sideways snap-in instability, thereby offering significantly greater actuation stroke compared to existing designs. Further improvement is achieved by reinforcing the individual beams in this flexure mechanism. While the traditional Paired Double Parallelogram (DP-DP) flexure design with comb gap G = 3 μm and flexure beam length L1= 1 mm results in a 50 μm stroke before snap-in, the reinforced C-DP-DP design with the same comb gap and flexure beam length achieves a stroke of 141 μm. Furthermore, this C-DP-DP flexure design provides a 215 μm stroke with G = 4 μm, and a 245 μm stroke with G = 6 μm. The presented work includes closed-form stiffness expressions for the reinforced C-DP-DP flexure, a design procedure for selecting dimensions of the overall comb-drive actuator, micro-fabrication of some representative actuators, and experimental measurements demonstrating the large stroke.
IEEE Journal of Microelectromechanical Systems (Journal of MEMs)


Actuator, comb-drive, flexure mechanism, large stroke
Created April 30, 2013, Updated February 19, 2017