A novel method of manufacturing three-dimensional ionic polymer–metal composites (IPMCs) biomimetic sensors, actuators and artificial muscles

All commercially available (as-received) perfluorinated ion-exchange polymers are in the form of hydrolyzed polymers and are semi-crystalline and may contain ionic clusters. The membrane form of these polymers has a typical thickness in the range of approximately 100–300 μm. Such a thin thickness of commercially available membranes permits fast mass transfer for use in various chemical processes. Although ionic polymer–metal composite (IPMC) artificial muscles made with these ion-exchange membranes have shown a great potential to produce large bending displacements in cantilever form and high force densities (maximum force greater than 40 times of its own weight), achieving large forces to be utilized in many practical devices requires manufacturing and fabrication of three-dimensional IPMCs. Knowing that such as-received semi-crystalline membranes are not melt-processable, they are not suitable for the fabrication of three-dimensional electroactive materials or other composite forms. In this work, the authors report a newly developed fabrication method that can scale-up or down the IPMC artificial muscles in a strip size of micro-to-centimeter thickness. We have adopted a recently developed technique by Moor et al. [J Membr Sci 75 (1992) 7] for dissolving as-received ion-exchange membranes in appropriate solvents. By carefully evaporating solvents out of the solution, recasted ion-exchange membranes were obtained. The test results showed that a successfully fabricated IPMC strip in a size of 2 mm thickness, 5 mm width, and 15 mm length, produces generative forces (tip forces) more than 20 gmf up to approximately a half centimeter-displacement under a small voltage.