Ionic polymer-metal composites (IPMCs) consist of a perfluorinated ionomer membrane (usually Nafion or Flemion) plated on both faces with a noble metal such as gold or platinum and neutralized with a certain amount of counterions that balance the electrical charge of anions covalently fixed to the membrane backbone. IPMCs are electroactive materials that can be used as actuators and sensors. Their electrical-chemical-mechanical response is highly dependent on the cations used, the solvent, the amount of solvent uptake, the morphology of the electrodes, and other factors. With water as the solvent, the applied electric potential must be limited to less than 1.3V at room temperature, to avoid electrolysis. Moreover, water evaporation in open air presents additional problems. These and related factors limit the application of IPMCs with water as the solvent. Glycerol has a viscosity of about 1000 times that of water at room temperature, and has a greater molecular weight. Like water, it consists of polar molecules and thus can serve as a solvent for IPMCs. We present the results of a series of tests on both Nafion-based IPMCs with glycerol as the solvent, and compare these with the results obtained using water. We also present the response of Nafion-based IPMCs with various cation forms treated with glycerol stimulated with suddenly applied and then sustained (DC) electric potentials in open air. IPMCs with glycerol as their solvent have greater solvent uptake, and can be subjected to relatively high voltages without electrolysis. They can be actuated in open air for rather long time periods. They may be good actuators when high-speed actuation is not necessary.
Ionic polymer-metal composites (IPMCs) consist of a perfluorinated ionomer membrane (usually Nafion or Flemion). The ionomer is plated on both faces with a noble metal such as gold or platinum. It is neutralized with a certain amount of counterions that balance the electrical charge of anions covalently fixed to the backbone membrane. IPMCs are electroactive materials that can be used as actuators and sensors. Their electrical-chemical-mechanical response is highly dependent on the cations used, the nature and the amount of solvent uptake, the morphology of the electrodes, and other factors. When a cantilever strip of solvated Nafion-based IPMC sample is subjected to a suddenly applied and sustained (DC) electric potential of several volts (1-3 V) across its faces, it bends towards the anode. For Nafion-based IPMCs with alkali metals, actuation towards the anode is followed by a slow back relaxation towards the cathode. If the electric potential is removed and the two electrodes are shorted during this back relaxation, the sample displays a fast bending deformation towards the cathode and then slowly relaxes back towards the anode, attaining a new equilibrium position generally distinct from its initial state. One way to change various phases of IPMC actuation is achieved by changing input potential. The electric potential inputs may be used to control the actuation of IPMCs. We present the results of a series of tests on Nafion-based IPMCs with ethylene glycol as solvent, actuated under electric potential inputs other than DC electric potential. We present experimental results for increasing ramp and sinusoidal electric potential waveforms.
Ionic polymer-metal composites (IPMCs) consist of a perfluorinated ionomer membrane (usually Nafion or Flemion) plated on both faces with a noble metal such as gold or platinum and neutralized with a certain amount of counterions that balance the electrical charge of anions covalently fixed to the membrane backbone. IPMCs are electroactive materials that can be used as actuators and sensors. Their electrical-chemical-mechanical response is highly dependent on the cations used, the solvent, the amount of solvent uptake, the morphology of the electrodes, and other factors. With water as the solvent, the applied electric potential must be limited to less than 1.3V at room temperature, to avoid electrolysis. Moreover, water evaporation in open air presents additional problems. These and related factors limit the application of IPMCs with water as the solvent. Ethylene glycol has a viscosity of about 16 times that of water at room temperature, and has a greater molecular weight. It is used as an anti-freeze. Like water, it consists of polar molecules and thus can serve as a solvent for IPMCs. We present the results of a series of tests on both Nafion- and Flemion-based IPMCs with ethylene glycol as the solvent, and compare these with the results obtained using water. IPMCs with ethylene glycol as their solvent have greater solvent uptake, and can be subjected to relatively high voltages without electrolysis. They can be actuated in open air for rather long time periods, and at low temperatures. They may be good actuators when high-speed actuation is not necessary.
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