Electrochemically controllable biomimetic actuator

Ionic Polymer-Metal Composites (IPMCs) are soft electroactive polymers based upon ion-exchange membranes. IPMC actuators are capable of operating in both water and air environments. The main objectives of this research are: (1) to investigate the fundamental issues regarding the actuation mechanism in connection with the relaxation problem associated with IPMCs; (2) to attain improved performance of an IPMC as an effective actuator; (3) to explore a new feature of IPMC operation for further applications.; A number of experimental techniques, including electrochemical and electromechanical analyses, were performed to investigate the actuation characteristics of IPMCs. The resulting data revealed that the relaxation phenomena of the IPMC actuators are primarily caused by the overpotential of the surface electrodes. Overpotential values of approximately +1 V were clearly noted for the platinum-IPMC. As an alternative solvent of IPMC, a room temperature ionic liquids (RTIL) was investigated. When an IPMC was solvated with an effective RTIL, it not only showed a much improved bending motion but also seemingly eliminated the relaxation phenomena. Within appropriate operating conditions, unwanted electrochemical reactions on the surface were not observed in the RTIL system. As a result, the efficiency of IPMCs in an RTIL system was significantly improved because the input power was mostly used in actuation. Further, a surface modification technique provoking the self-oscillatory motion of IPMCs was investigated. The platinum-IPMC showed a kinetically-driven oscillatory bending motion in the presence of small organic molecules under applied DC inputs. The general behavior of self-oscillatory IPMC was highly repeatable and showed regular periodic phenomena. The self-oscillatory behavior of IPMCs under specific conditions could be a useful means to minimize the use of complex electronics in many small-scale applications.; An analytical model, which accounts for the electrochemical and electromechanical phenomena of the self-oscillatory IPMC was developed using an equivalent circuit, beam theory, and surface chemistry. The physical phenomena of the system were described in coupled differential equations. Seemingly, the model can accurately predict the self-oscillatory and non-linear behavior of the IPMC actuator.