A novel design and fabrication of multilayered ionic polymer-metal composite actuators based on Nafion/layered silicate and Nafion/silica nanocomposites

Recently, we prepared Nafion/layered silicate and Nafion/silica nanocomposites and used them as starting materials in the fabrication of ionic polymer-metal composites (IPMCs). Experimental data indicated that Nafion/silica-based IPMCs exhibited almost three times higher blocking force with 200% larger displacement than the pure Nafion-based IPMC. On the other hand, due to the barrier property of well-dispersed silicate platelets, the response rate of Nation/layered silicate-based IPMCs under an electric voltage was lower than that of Nafion-IPMC. However, these samples showed a complete lack of relaxation, which appeared to be a good sign of a prolonged service life of IPMC. In this work, the high blocking force and the lack of relaxation during operation period observed, respectively, for Nafion/silica- and Nation/layered silicate-based IPMCs were combined in a multilayer configuration, which contained a main Nafion/silica nanocomposite layer sandwiched between two outer layers of Nafion/layered silicate nanocomposites. Two designs for multilayered IPMCs were proposed. In the first design, the electrode layer of IPMCs was prepared by a conventional electroless plating process, while in the second design a flexible electrode layer was made by recasting of a mixture containing Nation solution, layered silicate and a conductive material (e.g. Ag nano-powder). The multilayered IPMC exhibited a greatly improved blocking force with a very limited relaxation. The IPMC of the second design showed a blocking force of 6 and 9 g(r) at 2 and 3 V dc, respectively. A remarkable improvement in tip displacement of IPMC was also obtained, where multilayered IPMCs demonstrated a 250% increase in tip displacement compared to that of Nafion-IPMC. Furthermore, the response rate of multilayered IPMCs was also higher than that of conventional Nafion-based IPMC. Results and highlights of our present study are presented in this paper. (c) 2006 Elsevier B.V. All rights reserved.