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

Abstract

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 μm 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 × 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.

High Energy Density Capacitance Microgenerators

“…These devices are simple in production, and the technology earlier developed for smart sensors is used for their fabrication. For these devices the specific power of order 100 μW/cm 2 was reached [36]. The further increase of specific power is impeded by large interelectrode gaps used here, of order 20 μm.…”

“…They have rather large sizes (about 20*20 mm 2 ) and small specific power (of order 100 μW/cm 2 ) despite the fact that the value of power was considerably increased by means of multiple overlapping of strips in interdigitated comb structure (see [5]) of the generator with high displacements (of about 1 mm) in resonance mode of operation [36]. It should be noted that these devices have large interelectrode gaps (more than 20 μm), which prevent the essential decrease of the sizes of generators to reach the values needed for the microelectronics.…”

“…The case of lateral displacement of capacitor plates under the operation of electret generator in the current mode (see the scematic design in Fig.2c) should be emphasized particularly, because it is realized in practice, see, e.g., so-called "in-plane gap-closing" constructions [32][33][34][35][36] and the rotational systems [29]. This operation mode is described by following equations (see equation (12)):…”

“…In electret generators [16,17,[24][25][26][27][28][29][30][31][32][33][34][35][36] (see the circuits in Fig.1b,c and scematic designs in Fig.2a-c) the dielectric layer with built-in charge is formed on the inner surface of fixed plate of capacitor C(t) , and the charge losses are compensated by electrostatic induction of charge on the surface of moving plate, that is a considerable advantage of this way of energy transformation. These generators are further divided into current generators in which the capacitor C(t) is directly connected to the load R (see Fig.1b and …”

MEMS Technologies for Energy Harvesting

“…Among the materials most commonly used for electrets we find inorganic layers made of SiO 2 , a combination of SiO 2 and Si 3 N 4 layers, [52], and also organic compounds based on polymers. Among the polymers compatible with MEMS processes we may find the amorphous perfluorinated polymer CYTOP (Asahi Glass Col., Ltd), [53,54,55,56]. This polymer can provide up to four times more charge density than Teflon.…”