High performance bidirectional electrostatic inchworm motor fabricated by trench isolation technology

We report on an electrostatic linear micromotor, which employs built-in mechanical leverage to convert normal deflection of a flexible plate into a small in-plane step and two clamps to enable bidirectional inchworm motion. The motor, measuring 412 μm × 286 μm, is fabricated by a combination of trench isolation technology and standard surface micromachining in a relative simple process. The maximum achieved travel range was ±70 μm, limited only by flexure design. Depending on the plate actuation voltage, two operation modes, below and above pull-in of the plate, are demonstrated with an adjustable step size from 0.6 to 7 nm and 49 to 62 nm, respectively. The motor was driven in a broad cycling frequency range from 0 to 80 kHz. Output forces of 1.7 mN are measured at 55 V for both the clamps and plate. The motor was operated for 5 days at a stepping frequency of 80 kHz and has completed a cumulative distance of more than 1500 m in about 34·10⁹ steps without any performance deterioration.