MEMS electrolytic inchworms for movable neural probe applications

We have designed, fabricated, and tested an inchworm actuator using water electrolysis as the mechanical power source. The device was introduced in [1], and further characterization and interesting reliability results are reported here. Each actuator is made of two sealed electrolyte-filled silicone balloons. When electrolysis is run inside a balloon, the balloon expands due to gas generation. When electrolysis is stopped, the balloon shrinks due to gas recombination and permeation through the silicone. Bidirectional movement of a rotor, e.g., a metal probe, is obtained by applying specific expansion/shrinkage sequences to the balloons. The device works at low voltage and current, with peak power consumption around 100 μW. Displacement of silicon and metal probes from 0.5 μm to 75 μm per cycle was demonstrated. Reliability tests were also performed. The hydrogel-enabled process to fabricate the balloons is also illustrated.