Abstract
Ionic polymer membranes plated with platinum and gold serve as actuators when a small potential is applied. However, the water used to hydrate the membrane evapo rates during use, decreasing actuator performance. Ionic liquids are being consid ered as a replacement for water because of their low vapor pressure. Prior studies show that the large ion size and high viscosity of ionic liquids slow the response time of the polymer membrane when a voltage is applied. This study examines the relationships of ion size and viscosity to transduction by modeling ionic liquids with inexpensive salts of varying ion size and glycerol/water solutions. Based on these results several ionic liquids were selected and tested for use as membrane sol vents. This study includes frequency response, step response, and impedance tests of samples impregnated with Li + , K + , Cs + , TMA + , TEA + , and TBA + . Actuators solvated in solutions with a viscosity similar to 70–80 wt. % glycerol solutions (18–46 cP) and cation size similar to that of TMA + (0.347 nm) appear to yield the best results. When used as the membrane solvent, the ionic liquid 1-ethyl-3-methyl imidazolium tri fl uoromethanesulfonate (IL #3) resulted in the greatest strain per charge per area of the three ionic liquids tested in this study.
Highlights
Ionic polymer metal composites (IPMCs) are smart materials being in vestigated for applications as actuators and sensors
Of the three different ionic liquids tested as membrane solvents, those exhibiting suc cessful frequency response data had cations approxi mately the size of TMA+ and viscosities near that of 70 to 80 wt. % glycerol
The most effective ionic liquids were characterized by an ionic radius of approximately 0.347 nm and a viscosity between 18 and 46 cP
Summary
Ionic polymer metal composites (IPMCs) are smart materials being in vestigated for applications as actuators and sensors. These materials require low operation voltages of 1–5 V and act as simple mechanical devices. When an electric field is applied across the IPMC, the movement of cations and water molecules inside the membrane causes the actuator to bend toward the anode. The IPMCs are manufactured by plating an ionic polymer membrane with a thin layer of metal. The majority of work in this area uses a NafionTM polymer membrane plated with a thin layer of platinum metal, with a layer of gold metal to improve surface conductivity.[1, 2] Previous work established a procedure for manufacturing IPMCs with repeatable mechanical and electrical properties.[1]
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