Nafion-Pt IPMC electroactive behavior changes in response to environmental nonequilibrium conditions

摘要

Abstract Electroactive polymers (EAPs) continue to gain attention for their potential to offer unique and versatile solutions in the soft robotic and flexible electronic industries. Ionic polymer-metal composites (IPMCs) are a class of ionic-type EAPs which can be configured as capacitor actuators with very low voltage requirements (⩽5 V AC or DC). Their compact, portable, and lightweight properties, coupled with a biomimetic bending actuation response make them ideal for human-machine integrated technologies such as medical implants, active skins, and artificial muscles. This work tested the IPMC’s actuation and electrical response in varying saturation conditions (70% RH, 85% RH, 95% RH, and DI water liquid immersion) and voltage application schemes (direct current voltage (DCV) cycled, continuously applied, and relaxation responses upon voltage removal). This information was then used to establish actuation and back-relaxation response patterns through repetitive testing for statistical certainty. These demonstrated maximized actuation in water vapor conditions where the IPMC’s dielectric permittivity is maximized ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"><mml:msup><mml:mi>ε</mml:mi><mml:mrow><mml:mi mathvariant="normal">′</mml:mi></mml:mrow></mml:msup><mml:mo>≅</mml:mo><mml:mn>1.37</mml:mn><mml:mo>×</mml:mo><mml:mrow><mml:msup><mml:mn>10</mml:mn><mml:mn>6</mml:mn></mml:msup></mml:mrow></mml:math> ), and the dissipation factor is minimized ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"><mml:mrow><mml:mi>tan</mml:mi><mml:mi>δ</mml:mi><mml:mo>=</mml:mo><mml:mn>4.6</mml:mn></mml:mrow></mml:math> ). The response trends in vapor conditions are gradual but yield larger actuation ranges with increasing hydration. Liquid immersion restricts the IPMC’s range of motion but produces a sharper response pattern. These trends were validated against previously published IPMC actuator models. All of this creates a more pragmatic perspective on the potential of this technology which aids in the advancement of this material’s evolution towards viable real-world application configurations which capitalize on the material’s natural responses.