Surface micromachined linear electrostatic stepper motor

Abstract

A linear electrostatic stepper motor has been designed and fabricated in a single mask surface micromachining process.. It consists of two drive units that alternately generate a step to move the shuttle. The friction and adhesion in the clamps has been measured. A friction coefficient of 0.8 * 0.3 have been found. The adhesion in the clamp is just low enough to release the clamping shoe. Stepping cycles have been performed succesfully to obtain a deflection of 15 pm, with steps in the order of 2 pm. The deflection is limited by the suspension. The generated force equals 3 pN at 40 V driving voltage.

Static friction in elastic adhesion contacts in MEMS

“…However, the load forces in MEMS devices are often so small (pN's), that even in rough contacts the contribution of the adhesion forces to the total load compressing the surfaces can not be neglected [22]. The influence of adhesion, and its dependence on the surface roughness is therefore included in the elastic contact model.…”

High-Performance Shuffle Motor Fabricated by Vertical Trench Isolation Technology

“…The pull-in voltage is a function of the geometry of the plate and depends on the axial load S. For zero axial load, the pull-in voltage of the plate is given by [7]: A max is determined by the initial gap g a between the plate and the substrate minus the height of bumps (A max = g a − b). The length 2L f is the part of the plate that is not in contact with the substrate and depends on the applied voltage U p .…”

“…As a result, electrostatic microactuators with large displacement ranges generally suffer from low output forces. Electrostatic micromotors based on stepping motion [5][6][7][8][9][10][11][12][13] are a practical solution for generating large output forces and large displacements simultaneously. These motors use a "large force-short stroke" microactuator to produce small, powerful steps.…”

“…These motors use a "large force-short stroke" microactuator to produce small, powerful steps. A clamping mechanism, either based on frictional force [5][6][7][8][10][11][12][13] or obtained with gear teeth [9], is employed to create large displacements via incremental steps. In these motors, the propulsion and the clamping are dissociated to allow for individual optimization of these two mechanisms.…”

Static friction in elastic adhesive MEMS contacts, models and experiment

“…In order to test the clamps of a polysilicon stepper motor [22], a friction meter, similar to [37], has been fabricated. The friction as a function of the applied load has been measured.…”