Preparation And Properties Of The Patterned FEP Electret

As an energy harvest device, micro-electret generator is an ideal energy to replace the buttonbatteries, it convert mechanical energy into electrical energy, and it has a long working life and noharm to the environment. Institutions both at home and abroad have reported a number ofprototypes of micro-electret generator, these generators can be hardly putted into practiceapplication because the performance of the electret is not good enough. At present, electrets inmany generators are inorganic material like SiO2, although there’re many high-performancepolymeric materials(FEP, PTFE etc.), but they’re difficult to process. So the difficulty in the currentstudy is the preparation of high performance electret which is suitable for micro-generator. In thispaper, we have studied the properties of Teflon FEP electrets, and a patterned FEP electrets hasbeen gained successfully.The following are the main contents and results of this paper.(1). The Teflon FEP was charged under room temperature(about25℃),100℃,200℃respectively by corona charging. The effect of temperature on the charge storage stability of FEPelectret was investigated. High temperature during corona charging can improve the stability chargestorage stability of FEP. But in the AC corona mode, the charge stability was decreased with highcharging temperature.(2). Four corona mode were used for the charging of FEP, they were negative corona with DCpower, positive corona with DC power, positive corona with pulse power and corona with ACpower. We studied the relationship between corona mode and the charge stability of FEP electret.Samples with negative polarity had a better charge stability than those with positive polarity. Thecharge stability of the samples charged by pulse corona was higher than those charged by DCcorona mode. What’s more, we found that the polarity of the samples charged by AC corona modewere all negatively.(3). The charge storage mechanism of FEP electrets were analyzed using a thermallystimulated discharge (TSD) technique. By comparing the TSD spectrum, we found that samplescharged at room temperature had several current peak when the temperature was lower than100℃,but as we improved the charging temperature, these current peak began to shifted to hightemperature or even disappeared. The FEP electret with same polarity had a similar TSD spectrum,but the spectrums were very different when their polarities were diffenent.(4). Three methods were proposed to prepare a patterned FEP electret using a large piece of FEP. After charging experiments, we found that the thermal polarization could not be used tomaking a patterned FEP electret because the electric dipole was also polarized during the chargingprocess. By covering a patterned electrode on the FEP film was also improper because the dischargeof air gap between the film and patterned electrode. To depositing a patterned metal layer in thesurface of FEP film, a patterned FEP electret was made successfully.(5). Then the charge storage stability of patterned FEP electret was studied, the result showedthat the stability was not good. Because the patterned electrode increased the surface conductivityand activity of FEP, the charge stability became poor.(6). The width of the electrode also has an impact on the charge stability of FEP electret,charges in the surface of patterned FEP will diffuse or migrate to the electrode and then attenuated,as the width goes smaller, the pitch between the electrode also becomes smaller, the averagedistance for the charges move to the electrode becomes short, the charges is more prone to attenuate.When the width increasing, the charge stability will be improved.