The development of electrically driven mechanochemical actuators that act as artificial muscle

Abstract

Ras Labs, LLC, is committed to producing a variety of electroactive smart materials and actuators that are strong, resilient, and respond quickly and repeatedly to electrical stimuli over a wide temperature range. Cryogenic and high temperature experiments (4.22 K to 137°C) were performed on the contractile electroactive materials developed by Ras Labs with very favorable results. One of the biggest challenges in developing these actuators, however, is the interface between the embedded electrodes and the electroactive material because of the pronounced movement of the electroactive material. If the electroactive material contracts very quickly, the electrode is often left behind and thus becomes detached. Preliminary experiments explored the bonding between these electroactive materials with plasma treated metals provided by the Department of Energy's Princeton Plasma Physics Laboratory (PPPL) at Princeton University. The results were encouraging, with much better bond strengths in the plasma treated metals compared to untreated controls. Plasma treatments, and other treatments to non-corrosive metal leads, were further investigated in order to improve the attachment of the embedded electrodes to the electroactive material. Surface water drop contact angle tests, modified T-peel testing, and mechanical testing were used to test metal surfaces and metal-polymer interfaces for stainless steel and titanium. X-ray photoelectron spectroscopy (XPS) was used to determine the atomic surface composition of stainless steel and titanium after various plasma treatments. Mode of failure after T-peel testing and mechanical testing was determined using scanning electron microscopy (SEM) and stereo microscopy. Nitrogen plasma treatment of titanium produced a strong metal-polymer interface; however, oxygen plasma treatment of both stainless steel and titanium produced even stronger metal-polymer interfaces. Plasma treatment of the electrodes allows for the embedded electrodes and the electroactive material of the actuator to work and move as a unit, with no detachment, by significantly improving the metal-polymer interface.