Actuators

Geometric Manipulation and Analysis of Nafion-Based Ionic Polymer-Metal Composite (IPMC) Actuators for Mechanically Active Schemes

Ionic Polymer-Metal Composites (IPMCs), designed as electromechanical sensors and actuators, offer relatively large actuation displacement responses to their sensitivity to low applied voltages or mechanical strains. Currently, these materials are being proposed for use in applications in soft robotic actuators, artificial muscles, wearables, as well as dynamic sensors in response to mechanical stimuli. Still, measuring the strain of these electroactive materials is very challenging as the response of IPMCs may vary over time due to changes in temperature, humidity, and applied voltage. These areas have yet to be extensively investigated by researchers and a better understanding of the stability of these materials is required to move forward with this technology in realistic applications. The objective of this research is to investigate the pattern-ability of these thin-film actuators, as well as to characterize the change of electroactive response of the materials as a function of the above-discussed variables. This research is currently developing these IPMC actuator films (~50-150 μm thick) comprising of Nafion impregnated with dispersed platinum and/or silver nanoparticles in various geometries for dynamic flow control application schemes.
The displacement response has been measured in both cantilever and stacked actuator architectures so that both the lateral and longitudinal strain responses (due to the different clamped configurations) were measured in this work, correlating to the various configurations required for soft actuator and sensor applications. While being analyzed with the profilometer system, the IPMC actuators were subjected to a variety of voltage cycling tests and the resulting displacement responses were monitored. These included variations in the voltage applied, as well as the length of time of the applied voltage loading. Periodic thermal and electrical measurements were also conducted throughout cycling testing to produce further correlation between property changes and resulting performance trends, such as changes to the capacitance, dielectric, resistivity, and water content of the IPMC actuators as they were subjected to the various changes in humidity, temperature, and applied voltage. Resulting measurements and response trends were also compared between the Pt- and Ag- IPMCs, as well as with respect to the original (unaltered) Nafion material in both pre-fabricated membranes and dispersion-casting forms.