Considerations for contractile electroactive polymeric materials and actuators

Abstract

Ras Labs produces electroactive polymer (EAP) based materials and actuators that bend, swell, ripple and now contract (new development) with low electric input. This is an important attribute because of the ability of contraction to produce life-like motion. The mechanism of contraction is not well understood. Radionuclide-labeled experiments were conducted to follow the movement of electrolytes and water in these EAPs when activated. Extreme temperature experiments were performed on the contractile EAPs with very favorable results. One of the biggest challenges in developing these actuators, however, is the electrode-EAP interface because of the pronounced movement of the EAP. Plasma treatments of metallic electrodes were investigated in order to improve the attachment of the embedded electrodes to the EAP material. Surface analysis, adhesive testing, and mechanical testing were conducted to test metal surfaces and metal-polymer interfaces. The 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 EAP material of the actuator to work and move as a unit, with no detachment, by significantly improving the metal-polymer interface.

Reversible switching transitions of stimuli-responsive shape changing polymers

“…Electroactive ionic polymer-metal composite actuators are normally made from ion exchange polymer lms which are surface coated with noble metal electrodes. 412,413 As shown in Fig. 18, ion concentration between the two surfaces of the lm changes because of the ion transport in ion-water clusters if an electric eld is applied across the lm.…”

Considerations for contractile electroactive materials and actuators

“…Based on previous research following radionuclides, 27,35 contraction is due the net outflux of sodium ions to the externally placed negative electrode, which also causes a huge outflux of water molecules, virtually simultaneously, causing a rapid and profound contraction of the EAP. In selected formulations, when the polarity is reversed, rapid expansion of the EAP occurs, and the contraction-expansion can be cycled repeatedly.…”

“…Cross-linked, ion-containing electroactive polymeric (EAP) materials developed by Ras Labs have shown good results in terms of strength and electroactivity, 24,25 with the ability of some of these EAP materials to contract more than 80 % within 1 minute at 50 V, and then return to their original size and shape when the electric input is stopped, repeatedly. 26,27 Recently, stronger EAP materials were produced that quickly contract and then expand, repeatedly, by reversing the polarity of the electric input. The contractionexpansion cycles can be cycled repeatedly, lending these EAPs to applications where life-like motion is desired.…”

“…In our previous research, radionuclide-labeled electrolyte and tritium labeled water experiments were performed concurrently to definitively determine the chain of events that occur when the EAP materials developed by Ras Labs contract. 27,35 Molecular modeling further explored this phenomenon, followed by experimentation using different electrolyte solutions, pH considerations at the electrodes, and different ionic concentrations to determine exactly how and why contraction and expansion occur in these ion-containing EAPs.…”

Considerations for contractile electroactive materials and actuators

“…Based on previous research following radionuclides, 27,35 contraction is due the net outflux of sodium ions to the externally placed negative electrode, which also causes a huge outflux of water molecules, virtually simultaneously, causing a rapid and profound contraction of the EAP.…”