Temperature-dependent Ionic polymer-metal composite (IPMC) sensing dynamics: Modeling and inverse compensation

Ionic polymer-metal composites (IPMCs) have intrinsic sensing capabilities. Like many other sensing materials, however, IPMC sensors demonstrate strong temperature-dependent behaviors. In this paper we present the first systematic studies on temperature-dependent IPMC sensing dynamics. A cantilevered IPMC beam, soaked in a water bath with controlled temperature, is excited mechanically at its tip at frequencies of 10-100 Hz. The empirical frequency response of the sensor, with the tip displacement as input and the short-circuit current as output, shows clear dependence on the bath temperature. The sensing dynamics is modeled with a transfer function with temperature-dependent coefficients. By fitting the values of the coefficients at a set of test temperatures, we capture the temperature-dependence of the coefficients with polynomial functions, which can be used to predict the sensing dynamics at other temperatures. We further investigate the inversion of the sensing dynamics, for extracting the mechanical signal given the sensor output. In particular, a stable but noncausal inversion algorithm is applied to deal with the unstable zeros of the original sensing dynamics. Experimental results with both harmonic stimuli and free vibrations have validated the effectiveness of the proposed modeling and inversion schemes for IPMC sensors under different temperatures.