Polymer Electrolyte Actuator Driven by Low Voltage
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29 Mat. Res. Soc. Symp. Proc. Vol. 600 0 2000 Materials Research Society
I
CF CF- (CF 2(OCF 2CF 2)nCF)m-O(CF 2
2 )3 COO'Na+
CF 3
where m is 0 or 1. Fine glass powder was blown to the dry membrane with compressed air to roughen surface of the membrane. After washing and cleaning the surface, the membrane was boiled in water to swell. The swollen membrane was immersed in the aqueous ca. 10"2M solution of the gold complex to exchange ions for 12 hrs at room temperature. The impregnated cationic gold complex was reduced with the aqueous ca. 10"3M solution of Na2SO 3 at 40-70C. The cationic gold complex has the structure: The ion-exchange and reducing processes were repeated up to 8 times to make thick gold layers on the membrane. Sodium cation in the composite was exchanged with various alkali metal ions or alkylammonium ions by immersing the composite in aqueous chloride salt solutions for 12 hours at room temperature. Tubes of perfluorocarboxylic acid resin were plated only on outside by the same process as the membranes. The plated electrode was cut into four parts as shown in Figure 7 with an excimer laser abrasion process.
Al~
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Waveform Generator and Potentiostat Polymer Electrolyte-Au
SClowComposite
Sample
Laser Displacement Meter MN
A
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Wate
Laser Beam
Figure 1: A schematic of
Figure 2: A schematic of the set-
interfacial reduction process to plate gold electrode.
up for evaluating bending response.
Figure 2 is a schematic of the set-up for evaluating bending response. The plated polymer electrolyte was cut into a ribbon of 1 mm width and 8 mm length. The ribbon was supported vertically in water by clumping in platinum foil to make electric contact with the gold electrode.
Electric signals were supplied from a Yokogawa AG1200 waveform generator and a Hokuto Denko HA-501G potentiostat/galvanostat Displacement of the free end at a distance of 5 mm from the fixed point was measured by a Keyence LC-2220/2 100 laser displacement meter directed
through the glass sample cell at room temperature. Repeated cycles of ion exchange and reduction resulted in dendritic growth of. To evaluate the surface area capacitance of electric double layer was measured on the samples plated multi times. The capacitance increased with the number of the cycles almost in proportion. The surface area of the interface between electrode and polymer electrolyte is proportional to the capacitance. 230
Typical waveforms of current and displacement response of the composites driven by step voltage are shown in Figures 3. The sample is sodium perfluorosulfonate (Nafion® 117) with Pt electrodes. The complex waveform indicates multiple mechanism for the response. The first action is very fast and the peak appears within 10 ms after the step signal. We call this response as "quick action". The quick action decays in a few seconds. After ca. 5 seconds the second peak toward the cathode appears in this case. We call this response as "slow action". The slow action also decays in a minute. The direction of the quick ac
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