A new SOI/elastomer fabrication process that integrates a soft elastomer in-plane with silicon features has been developed, characterized and demonstrated. The simple three-mask process uses deep reactive ion etching of trenches in a silicon-on-insulator wafer to pattern high-aspect-ratio silicon and elastomer features from 2 μm to hundreds of micrometers in width. The elastic and adhesive properties of the fabricated elastomer have been characterized. A Young's modulus of 1.4 MPa was measured at moderate strains up to 75%, and nonlinear strain was observed beyond that. The SOI/elastomer process has been used to fabricate micromechanical thrusters to repeatedly store and release 1.3 μJ to propel a 2 mg 1.6 mm by 0.8 mm by 0.45 mm projectile 1.35 cm.

A new motor architecture that uses in-plane electrostatic gap-closing actuators along with a flexible driving arm mechanism to improve motor force density is introduced, optimized, manufactured, and tested. This motor operates similarly to other inchworm-based microactuators by accumulating small displacements from the actuators into much larger displacements in the motor. Using an analytical model of the inchworm motor based on the static force equilibrium condition, optimizations of a full motor design were performed to maximize motor force density. In addition, force losses from supporting flexures were included to calculate the theoretical motor efficiency for different motor designs. This force density optimization analysis of the gap-closing actuators and supporting motor structures provided the basis for designing and manufacturing inchworm motors with flexible driving arms and gap-closing actuators. The motor required only a single-mask fabrication and demonstrated robust performance, a maximum speed of 4.8 mm s−1, and a maximum force on the shuttle of 1.88 mN at 110 V which corresponds to area force density of 1.38 mN mm−2. In addition, instead of estimating motor force based on drawn or measured dimensions which often overestimates force, the demonstrated maximum motor force was measured using calibrated springs. The efficiency of the manufactured motor was measured at 8.75% using capacitance measurements and useful work output.

This paper presents the in situ characterization of microscale poly(dimethylsiloxane) (PDMS) springs using silicon-on-insulator-microelectromechanical systems (SOI-MEMS). PDMS samples that were 30 μm long, 20 μm thick, and 6 μm wide were fabricated on-chip along with a test mechanism that included electrostatic comb drive actuators and silicon flexures. The test mechanism allowed for applying strains up to 65%. The in situ test results were compared with results of tests on macroscale samples performed using a dynamic mechanical analyzer. The results imply that the process steps during fabrication initially led to increased crosslinking of the PDMS but that the final release of the structure in buffered hydrofluoric acid decreased the crosslink density, thereby decreasing the stiffness of the PDMS. Several implications of the results on processing PDMS in MEMS are presented. The results of this work are important for the design of MEMS devices which incorporate PDMS as a mechanical material.

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All-polymer dielectric elastomer actuators have been manufactured using a micro-molding fabrication process. The actuators are multilayer beams made of three conductive and two dielectric elastomer layers. By applying an electrical potential between two of the neighboring conductive electrodes, a stress is generated, which leads to an asymmetric axial strain and, therefore, bending. Bidirectional actuation is achieved by changing the pair of electrodes across which the potential is applied. A 100 μm wide, 40 μm thick, and 1000 μm long actuator demonstrated tip displacement as high as 318 μm at 1.1 kV with an electrical power consumption of 10 μW. Experimental results validate a two-dimensional ANSYS model that is also used to explore the effects of further decreasing layer thickness and relative electrode thickness on DEA performance.