The development of a high-performance perfluorinated polymer electret and its application to micro power generation

Recently, micro power generation using electrets has attracted much attention due to its large power output at a low frequency range. Since the theoretical power output is proportional to the square of the surface charge density of the electret, the development of a high-performance electret is required. In the present study, it is shown that the surface charge density of a CYTOP electret is significantly improved by the addition of terminal groups. Based on this fact, a novel high-performance polymer electret has been developed by doping a silane-coupling reagent into the polymer. A series of measurements of surface potential and TSD ( thermally stimulated discharge) spectra was made for various CYTOP films prepared with different silane-coupling reagent concentrations. It is found that the surface charge density, charge stability and thermal resistibility of electric charges are markedly improved by the doping. A surface charge density of 1.5 mC cm(-2), which is three times larger than that of Teflon AF, has been obtained on a 15 mu m thick film. In addition, the thermal stability of the CYTOP electret is superior to that of Teflon AF. Power generation experiment is also performed using the patterned CYTOP electret of 20 x 20 mm(2). At a low seismic frequency of 20 Hz, 0.7 mW power generation has been accomplished, which is about 2.5 times higher than our previous result.