Experimental and theoretical investigation of ionic polymer transducers in shear sensing

Abstract

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.

Electromechanical Evaluation of Ionomeric Polymer-Metal Composites Using Video Analysis

“…Furthermore, since the electrical conductivity of the solution inside the Nafion depends on the species present in the ionomeric channels, the resistivity of the IPMC is also affected and, consequently, the resistive-capacitive response of the device. Some authors found that the capacitive properties mainly dominate the electromechanical response of IPMCs [31][32][33] .…”

“…Bonomo et al 34 developed a circuit model to describe the IPMC electrical behavior, explaining that the electric charge accumulation causes the device flexural motions at the anode after an electrical potential is applied. Kocer et al 32 that the primary influence of the capacitive component of IPMC is related to its mechanical response. The stored electrical charge (Q) in the device after voltage application can be calculated by integrating the electric current as a function of time.…”

Ionic polymer metal composite compression sensors with 3D-structured interfaces

“…Variability and inconsistency, in turn, demand extensive property and performance characterization of each individual IPMC sample before use in any sensor system. Furthermore, until recent advancements [19][20][21][22], the limited understanding of the fundamental nature of material response to non-bending deformation in IPMCs has effectively precluded major breakthroughs in the development of non-bending mode sensors. In particular, a theoretical explanation of the compression sensing mode (electrical transduction of deformation in the thickness direction due to applied pressure normal to the electrodes) was only offered in 2017 in [22] and therein attributed to inhomogeneous strain through the IPMC thickness.…”

Modelling compression sensing in ionic polymer metal composites

“…This phenomenon is manifested through a short circuit current that is a function of the imposed displacement, modulated by strain magnitude and rate. The effectiveness of IPMCs in compression sensing has been formerly investigated in [48] and recently established in [49], opening the door for new, multimodal sensing applications combining traditional benders with shear and compression sensors [50,51].…”