NDLI: Mitigating IPMC Back-Relaxation Effect Through Controlled Activation of Patterned Electrodes

Content Provider	The American Society of Mechanical Engineers (ASME) Digital Collection
Author	Fleming, Maxwell Hubbard, Joel Kwang, J. Kim Kam, K. Leang
Copyright Year	2011
Abstract	With low driving voltage (<5V) and the ability to be operated in aqueous environments, ionic polymer-metal composite (IPMC) materials are quickly gaining attention for use in underwater applications. There are, however, drawbacks to IPMCs, including the “back relaxation” effect. Specifically, when subjected to a DC input (or an excessively slow dynamic input), the IPMC actuator will slowly relax back toward its original position. There is debate over the physical mechanism of back relaxation, although one prevalent theory describes an initial current, caused by the electrostatic forces of the charging electrodes, which drives water molecules across the ion-exchange membrane and deforms the IPMC. Once the electrodes are fully charged, however, the dominant element of the motion is the osmotic pressure, driving the water molecules back to equilibrium, thus causing back relaxation. A new method to mitigate back relaxation is proposed, taking advantage of controlled activation of patterned (sectored) electrodes on the IPMC. Whereas previous approaches to correct back relaxation rested on an increase of input voltage which can lead to electrolysis, subsequently damaging the material, this method involves only proper control of isolated electrodes to compensate for the back relaxation and does not require sensor feedback. An electromechanical model of the actuator is used to guide the design of these input signals, and the feasibility of using electrode patterning to mitigate back relaxation is demonstrated. Without reaching electrolysis, an IPMC is able to maintain its position for approximately 30 seconds. Compared to a simple step response, the rate of relaxation is reduced by 94% and the maximum error is reduced by 64%.
Sponsorship	Aerospace Division
Starting Page	65
Ending Page	72
Page Count	8
File Format	PDF
ISBN	9780791854723
DOI	10.1115/SMASIS2011-4970
Volume Number	ASME 2011 Conference on Smart Materials, Adaptive Structures and Intelligent Systems, Volume 2
Conference Proceedings	ASME 2011 Conference on Smart Materials, Adaptive Structures and Intelligent Systems
Language	English
Publisher Date	2011-09-18
Publisher Place	Scottsdale, Arizona, USA
Access Restriction	Subscribed
Subject Keyword	Water Relaxation (physics) Actuators Membranes Equilibrium (physics) Metals Pressure Electrodes Design Errors Composite materials Electrolysis Feedback Sensors Signals Ion exchange Polymers
Content Type	Text
Resource Type	Article

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