2-Paper Hilton

This paper presents in-plane electrostatic comb-drive actuators with stroke as large as 245 μm that is achieved by employing a novel Clamped Paired Double Parallelogram (C-DPDP) flexure mechanism. For a given flexure beam length, comb gap, and actuation voltage, this is currently the largest comb-drive actuator stroke reported in the literature. The C-DP-DP flexure mechanism design offers high bearing direction stiffness while maintaining low motion direction stiffness over a large range of motion direction displacement. The high stiffness ratio between the bearing and motion directions mitigates the on-set of sideways snap-in instability, thereby offering significantly greater actuation stroke compared to existing designs. INTRODUCTION Electrostatic comb-drive actuators have been used in various applications such as resonators [1], and micro/nano positioning [2]. A linear in-plane electrostatic comb-drive actuator, shown in Fig. 1, comprises two electrically isolated conductive combs with N fingers each. While the static comb is fixed with respect to ground, the moving comb is guided by a flexure mechanism so that it can displace primarily in Y direction (or motion direction) with respect to the static comb. These static and moving comb fingers (length Lf, in-plane thickness Tf, out-of-plane thickness Hf) have a nominal inter-digitation gap of G and an initial engagement of Yo. In general, the flexure mechanism is designed to provide linear displacement (Y) with relatively small stiffness (Ky) in the Y direction. Additionally, it provides minimal error motions (Ex) and relatively high stiffness (Kx) in the X direction, or bearing direction. In an ideal scenario, Ky and Ex would approach zero while Kx would approach infinity. However, in practice, this is never the case given the performance tradeoffs between motion range, stiffness, and error motions that exist in flexure mechanisms [3]. G-X G+X Lf X Stator Comb