Artificial Muscle Membranes Fabricated Using Ultra-Short Pulse Laser Ablation

An Ultra Short Pulse (USP) laser has been used for surface milling of dielectric elastomer actuator (DEA) polymer (3M VHB tape). DEA’s, artificial analogues to natural muscle, act as flexible capacitors and consist of a polymeric dielectric membrane material sandwiched between flexible electrodes. Actuation is in part determined by the voltage difference across the electrodes and the dielectric membrane thickness. Prior to the present report, pre-stretching the membrane provided the sole means for controlling membrane thickness. Good quality ablation, without grossly observable thermal damage, was achieved at removal rates of 0.0047 mm³/s using a 250 kHz repetition rate and an energy delivery of 2 μjoules/pulse. The surface milling operation was performed as a set of parallel passes produced a series of small shallow trenches, the result of overlap between subsequent passes of the laser. These features did not significantly compromise performance of the test actuators and the USP machined polymer could be pre-stretched at least five times the original size without rupture. When placed in a support frame and subjected to high electric field strength the stretched membrane also maintained its relatively high breakdown strength. A proof of concept two-thickness actuator, one half of it milled, was produced and successfully actuated. USP laser processing has provided a design freedom, beyond pre-stretching, and has opened the way to novel variable thickness micro-actuators.