Prediction of the ionic polymer transducer sensing of shear loading

While ionic polymer transducers (IPTs) have often been studied as actuators, they also show considerable promise as sensors. In addition to responding to bending, IPT sensors can also detect compression, tension and shear. Existing IPT models focus primarily on actuation, while the few available sensing models are limited to bending. This is due in part to the lack of a viable hypothesis for a physical mechanism that can explain the existence of a sensing signal in all deformation modes. Identification of the fundamental sensing mechanism is desirable as it could ultimately be exploited to design IPT sensors with an optimized response. Here it is hypothesized that the dominant physical mechanism for sensing is streaming potential, as it holds promise for explaining the existence of IPT sensing in any mode of deformation. We present a model for predicting the current developed when an IPT is subject to shear deformation, the creation of which has previously been elusive. The presented study employs a finite element approach to predict diluent flow with respect to the surrounding hydrophobic amorphous region under shear loading. Assessment of multiple flow path orientations with respect to load is used to impose volume averaging, and subsequently to project transducer current. Both peak and transient response are considered. Model predictions compare well with previously reported experimental results.