Freeform fabrication of ionomeric polymer-metal composite actuators

Purpose - To seek to produce low-voltage, soft mechanical actuators entirely via freeform fabrication as part of a larger effort to freeform fabricate complete electromechanical devices with lifelike and/or biocompatible geometry and function. Design/methodology/approach - The authors selected ionomeric polymer-metal composite (IPMC) actuators from the literature and the authors' own preliminary experiments as most promising for freeform fabrication. The authors performed material formulation and manual device fabrication experiments to arrive at materials which are amenable to robotic deposition and developed an SFF process which allows the production of complete IPMC actuators and their fabrication substrate integrated within other freeform fabricated devices. The authors freeform fabricated simple IPMC's, explored some materials/performance interactions, and preliminarily characterized these devices in comparison to devices produced by non-SFF methods. Findings - Freeform fabricated IPMC actuators operate continuously in air for more than 4 h and 3,000 bidirectional actuation cycles. The output stress scaled to input power is one to two orders of magnitude inferior to that of non-SFF devices. Much of this difference may be associated with process-sensitive microstructure of materials. Future work will investigate this performance gap. Research limitations/implications - Device performance is sufficient to continue exploration of SFF of complete electromechanical devices, but will need improvement for broader application. The feasibility of the approach for producing devices with complex, non-planar geometry has not been demonstrated. Practical implications - This work demonstrates the feasibility of freeform fabricating IPMC devices, and lays groundwork for further development of the materials and methods. Originality/value - This work constitutes the first demonstration of complete, functional, IPMC actuators produced entirely by freeform fabrication.