Electromechanical transduction in multilayer ionic transducers

Abstract

A transducer consisting of multiple layers of ionic polymer material is developed for applications in sensing, actuation and control. A multilayer transducer is fabricated by layering individual transducers on top of one another. Each multilayer transducer consists of two to four individual layers each approximately 200 µm thick. The electrical characteristics of the transducers can be varied by connecting the layers in either a parallel arrangement or a series arrangement. The tradeoff in deflection and force is obtained by controlling the mechanical constraint at the interface. Packaging the transducer in an outer coating produces a hard constraint between layers and reduces the deflection with a force that increases linearly with the number of layers. This configuration also increases the bandwidth of the transducer. Removing the outer packaging produces an actuator that maintains the deflection of a single layer with an increased force output. This is obtained by allowing the layers to slide relative to one another during bending. Experiments on transducers with one to three layers are performed and the results are compared to an equivalent circuit model which was modified to accommodate multilayer transducers. The modification is performed on four different boundary conditions: two electrical, the series and the parallel connection, and two mechanical, the zero interfacial friction and the zero slip on the interface. Expressions for blocked force, free deflection, and electrical impedance of the transducer are developed in terms of fundamental material parameters, transducer geometry, and the number of individual layers. The trends in the transducer response are validated using experiments on transducers with multiple polymer layers.

Layer-by-layer self-assembled conductor network composites in ionic polymer metal composite actuators with high strain response

“…[4][5][6][7] Since then, much research effort has been devoted to this class of EAPs with the objective of further improving the electromechanical performance properties such as the actuation speed, strain level, and efficiency. [4][5][6][7][8][9][10][11][12][13][14] Figure 1͑a͒ illustrates schematically such an ionic polymer bending actuator in which the accumulation and depletion of cations at the cathode and anode, respectively, create bending of the ionic polymer membrane under an electrical signal. Experimental results have indicated that a high population of the excess charges at the electrodes is highly desirable in order to generate high electromechanical actuation.…”

“…To realize that, porous electrodes which offer large electrode areas in contact with ionomers are often utilized in this class of actuators. [4][5][6][7][8][9][10][11][12][13][14] One widely investigated ionic polymer metal composite ͑IPMC͒ uses a chemical reduction method to deposit precious metals to Nafion ͑a perfluorosulfonated ionomer developed by DuPont͒ membrane surfaces, in which nanosized metal particles penetrate into the Nafion membrane to form porous electrodes. [5][6][7]11,14 More recently, a direct assembly method in which conductive nanoparticles were mixed with a Nafion ͑or an ionomer͒ solution and this mixture is directly deposited on the Nafion ͑or an ionomer͒ membrane to fabricate IPMC was developed.…”

“…[5][6][7]11,14 More recently, a direct assembly method in which conductive nanoparticles were mixed with a Nafion ͑or an ionomer͒ solution and this mixture is directly deposited on the Nafion ͑or an ionomer͒ membrane to fabricate IPMC was developed. 8,9,12,13 The direct assembly method to fabricate IPMCs is attractive because it allows for the use of a broad range of nanosized conductors for the electrodes such as carbon nanotubes. 13 It also simplifies the fabrication process of IPMCs and enhances actuator manufacturing repeatability.…”

“…8,9,12,13 The direct assembly method to fabricate IPMCs is attractive because it allows for the use of a broad range of nanosized conductors for the electrodes such as carbon nanotubes. 13 It also simplifies the fabrication process of IPMCs and enhances actuator manufacturing repeatability. 8,9,12,13 Illustrated in Fig.…”

“…13 It also simplifies the fabrication process of IPMCs and enhances actuator manufacturing repeatability. 8,9,12,13 Illustrated in Fig. 1͑b͒ is a typical bimorph ͑bending͒ actuator thus developed, which in general has a three layer structure, i.e., two porous composite electrode layers, which are referred to as the conductor network composite ͑CNC͒ and generate strain under applied voltage, separated by a neat ionomer layer.…”