Highly Enhanced Force Generation of Ionic Polymer–Metal Composite Actuators via Thickness Manipulation

On purpose to enhance the generating force of ionic polymer–metal composite (IPMC) actuators, the thickness of the ion-exchange membrane is manipulated in two different ways. One is grafting poly­(styrenesulfonic acid) onto poly­(vinylidene fluoride-<i>co</i>-hexafluoropropylene) films with varying thickness, and the other is stacking pre-extruded Nafion films to thicker films by pressing at high temperatures. For both groups of the membranes, ionic properties including ion-exchange capacity and ionic conductivity are maintained similarly inside the groups regardless of the thickness. The actuation tests clearly show the increase in generating force with increasing thickness of the IPMCs prepared. It is due to a larger bending stiffness of thicker IPMCs, which is consistent with the predicted result from the cantilever beam model. The increase in force is more remarkable in Nafion-stacked IPMCs, and a thick IPMC lifts a weight of 100 g, which far exceeds the reported values for IPMCs

High-Performance Electroactive Polymer Actuators Based on Ultrathick Ionic Polymer–Metal Composites with Nanodispersed Metal Electrodes

Ionic polymer–metal composites (IPMCs) have been proposed as biomimetic actuators that are operable at low applied voltages. However, the bending strain and generating force of the IPMC actuators have generally exhibited a trade-off relationship, whereas simultaneous enhancement of both the qualities is required for their practical applications. Herein, a significant improvement in both the strain and force of the IPMC actuators is achieved by a facile approach, exploiting thickness-controlled ion-exchange membranes and nanodispersed metal electrodes. To guarantee a large generating force of the IPMC actuators, ultrathick ion-exchange membranes are prepared by stacking pre-extruded Nafion films. Metal electrodes with a nanodispersed structure are formed on the membranes via alcohol-assisted electroless plating, which allows increased capacitance and facilitated ion transport. The resulting actuators exhibit greatly enhanced electromechanical properties, including an approximately four times larger strain and two times larger force compared to those of actuators having the conventional structure. Moreover, the ability to lift 16 coins (a weight of 124 g) has been successfully demonstrated using ultrathick IPMC actuators, which shows great promise in realizing artificial muscles