Experimental and theoretical investigation of ionic polymer transducers in shear sensing

Ionic polymer transducers (IPTs), sometimes referred to as ionic polymer metal composites, are ionomers that are plated with conductive media such as metals enabling both actuation and sensing behavior. As sensors they are most often studied in bending mode; however, a measurable signal can be generated in any mode of mechanical deformation. The fundamental physical mechanism responsible for IPT sensing is an open topic. This report asserts that a reasonable mechanistic model should be able to explain IPT sensing in any mode of deformation; the specific hypothesis offered here is the streaming potential hypothesis. In this paper, mathematical modeling of IPTs in shear sensing is presented in comparison with experiments. The experimental studies introduce a novel shear test apparatus for step-loading shear deflection and in situ measurement of resulting transient IPT current. The modeling estimations and experimental outcomes show good agreement, in terms of current output variation for imposed shear deformation magnitude, moreover, in the optimum metal particulate loading in the electrode layers leading to maximum shear sensitivity. The optimum metal concentration was determined to be in the vicinity of 40% for metal particulates by volume demonstrating the influence of electrode structure on the sensing response.