Direct assembly process: a novel fabrication technique for large strain ionic polymer transducers

Ionic polymer transducers (IPT) consist of an ion-exchange membrane plated with flexible conductive electrodes on their outer surface. Compared to other types of electromechanical transducers, ionomeric transducers have the advantage of high-strain output (> 9%), low-voltage operation (< 5 V), and high sensitivity in the charge-sensing mode. A novel fabrication technique for ionic polymer transducers named the Direct Assembly Process (DAP) was developed in this paper. The DAP allows the use of any type of ionomer, diluent, and conducting powder in the transducer, and permits the exploration of any novel ionomeric design. In this paper the effect of diluent content of the IPT, electrode thickness, and composition were optimized in term of maximum peak strain and strain rate generated by an IPT. Decreasing viscosity and increasing polarity and content of the diluent were demonstrated to increase the strain rate of an IPT. The thickness of the electrode was varied and correlated with the maximum strain generated due to a 2 V step input. This study also demonstrated that RuO2 composition has an optimal loading of 42 vol%, while SWNT electrodes have an optimal performance at around 30 vol%.