Multiphysics modeling of self-oscillations of ionic polymer gel actuators

When the electrocatalyst, platinum, was coated on polyelectrolyte gel surfaces and was immersed into an acidic formaldehyde (HCHO) solution, an input direct current (DC) current would produce oscillatory voltages on the surfaces of the ionic-polymer-metal-composites (IPMC) actuator. The oscillatory voltages on the two electrodes caused the concurrent migration of counter-ion clusters, and ultimately a self-oscillatory bending of the gel actuator was realized. To model the complex multiphysics processes involved in this gel actuator with a typical large length-to-height ratio, the electrochemical processes occurred along each cross section through the height were regarded identically as a one-dimensional process, and the mechanical deformation of the actuator was simplified as the bending of a beam. Motivated by the development of micro-grippers and tactile sensors, self-oscillations of gel actuator with variable cross sections and subject to a spring constraint were simulated for the first time. The procedure outlined herein presents a versatile framework for the design, analysis and optimization of self-oscillating gel actuators.