Modeling of electromechanical charge sensing in ionic polymer transducers

A model for charge sensing due to imposed deformation in ionic polymer materials is presented. The basic concept of this model is that mechanical deformation induces charge at the surface of the polymer and produces a measureable discharge of current as the material is deformed. This discharge of current occurs when a short-circuit electrical boundary condition is applied across the material electrodes. An expression for charge density, electric field and electric potential under short-circuit conditions is developed from the electrostatic field equations. The solution for charge density is coupled with the mechanical deformation through a proportionality constant. Expressions for induced charge and current flow are then derived from the equations for electric displacement at the surface of the material. Experimental results support the basic form of the model and also demonstrate that the geometric scaling predicted in the model agrees with measured data. Analysis of the length scale predicted by the model produces qualitative agreement with previously published results but also points to the need for a greater understanding of the interfacial mechanics in the ionic polymer transducers. (C) 2003 Elsevier Ltd. All rights reserved.