Electromechanical transduction in multilayer ionic transducers

Abstract

A transducer consisting of multiple layers of ionic polymer material is developedfor applications in sensing, actuation and control. A multilayer transducer isfabricated by layering individual transducers on top of one another. Eachmultilayer transducer consists of two to four individual layers each approximately200 µm thick. The electrical characteristics of the transducers can be varied by connecting thelayers in either a parallel arrangement or a series arrangement. The tradeoff in deflectionand force is obtained by controlling the mechanical constraint at the interface. Packagingthe transducer in an outer coating produces a hard constraint between layers and reducesthe deflection with a force that increases linearly with the number of layers. Thisconfiguration also increases the bandwidth of the transducer. Removing the outerpackaging produces an actuator that maintains the deflection of a single layer with anincreased force output. This is obtained by allowing the layers to slide relative to oneanother during bending. Experiments on transducers with one to three layers are performedand the results are compared to an equivalent circuit model which was modified toaccommodate multilayer transducers. The modification is performed on four differentboundary conditions: two electrical, the series and the parallel connection, andtwo mechanical, the zero interfacial friction and the zero slip on the interface.Expressions for blocked force, free deflection, and electrical impedance of thetransducer are developed in terms of fundamental material parameters, transducergeometry, and the number of individual layers. The trends in the transducer responseare validated using experiments on transducers with multiple polymer layers.