New DRIE-Patterned Electrets for Vibration Energy Harvesting

This paper is about a new manufacturing process aimed at developing stable SiO2/Si3N4 patterned electrets using a Deep Reactive Ion Etching (DRIE) step for an application in electret-based Vibration Energy Harvesters (e-VEH). This process consists in forming continuous layers of SiO2/Si3N4 electrets in order to limit surface conduction phenomena and is a new way to see the problem of electret patterning. Experimental results prove that patterned electrets charged by a positive corona discharge show excellent stability with high surface charge densities that may reach 5mC/m^2 on 1.1\mu m-thick layers, even with fine patterning and harsh temperature conditions (up to 250{\deg}C). This paves the way to new e-VEH designs and manufacturing processes.Comment: Proc. European Energy Conference, 201

Research and development of miniaturized electrets

A description is given of the realization of small electrets, using techniques generally applied in the fabrication of integrated circuits and microsensors. Attention is paid to the different electret decay mechanisms and their relative contributions to the overall stability of miniaturized electrets. A process is described by which polymer electrets such as Teflon-FEP and PTFE (polytetrafluoroethylene) can be deposited and shaped in a predefined pattern on a silicon wafer. Results on the application of new materials, especially silicon dioxide (SiO2), for use in electret applications, are presented. It appears that after an appropriate treatment of the oxide surface, its charge-stability is at least equal to that of polymer electrets such as Teflon-FEP and PTF

Electrets used to measure exhaust cloud effluents from Solid Rocket Motor (SRM) during demonstration model (DM-2) static test firing

Electrets were compared with fixed flow samplers during static test firing. The measurement of the rocket exhaust effluents by samplers and electrets indicated that the Solid Rocket Motor had no significant effect on the air quality in the area sampled. The results show that the electrets (a passive device which needs no power) can be used effectively alongside existing measuring devices (which need power). By placing electrets in areas where no power is available, measurements may be obtained. Consequently, it is a valuable complementary instrument in measuring rocket exhaust effluents in areas where other measuring devices may not be able to assess the contaminants

Electrets and their application in contamination studies

Data are presented on the surface charge of many different types of electrets formed by several different techniques. Results are presented on the investigation of electrets as pollution control devices for their possible use in the control of a spacecraft environment

Experimental research in the use of electrets in measuring effluents from rocket exhaust and a review of standard air quality measuring devices

Seven standard types of measuring devices used to obtain the chemical composition of rocket exhaust effluents were discussed. The electrets, a new measuring device, are investigated and compared with established measuring techniques. The preliminary results obtained show that electrets have multipollutant measuring capabilities, simplicity of deployment, speed of assessment or analysis, and may be an important and valuable tool in measuring pollutants from space vehicle rocket exhaust

The application of silicon dioxide as an electret material

The authors have investigated silicon dioxide for its electret properties. It appears that thermally grown silicon dioxide has a large lateral surface conductivity, resulting in poor electret behavior. This can be adequately reduced by chemical surface modification, resulting in an excellent silicon dioxide electret. Experiments have shown that corona-charged SiO2 layers are much more resistant to high temperatures than Teflon-FEP electrets. A 1.1-¿m-thick SiO2 layer, charged up to 150 V, yields a time constant of the charge decay in excess of 400 yr at ambient laboratory condition

Study of the charge profile of thermally poled electrets

The charge profile of thermally poled electrets has been studied using two different methods, laser induced pressure pulse (LIPP) and pulsed electroacoustic (PEA), to gain insight into the mechanisms that are activated and assess which is the most appropriate method to study the charge profile. Disc--shaped PET samples have been conventionally poled to activate both the alpha and the rho relaxation and, right after, partially discharged up to a temperature Tpd. In this way, samples with a different combination of dipolar and space charge polarization have been obtained. Both LIPP and PEA reveal asymmetric profiles for Tpd below the glass transition temperature, that progressively become antisymmetric for higher temperatures. The shape and evolution of the charge profiles can be explained assuming injection of negative carriers from the anode that enhances the trapping of positive carriers near this electrode. It can be observed that PEA is able to detect a wider variety of polarization mechanisms in the system while LIPP gives a simpler picture of the charge profile.Comment: 19 pages, 11 figure

Parylene-based electret power generators

n electret power generator is developed using a new electret made of a charged parylene HT® thin-film polymer. Here, parylene HT® is a room-temperature chemical-vapor-deposited thin-film polymer that is MEMS and CMOS compatible. With corona charge implantation, the surface charge density of parylene HT® is measured as high as 3.69 mC m^−2. Moreover, it is found that, with annealing at 400 °C for 1 h before charge implantation, both the long-term stability and the high-temperature reliability of the electret are improved. For the generator, a new design of the stator/rotor is also developed. The new micro electret generator does not require any sophisticated gap-controlling structure such as tethers. With the conformal coating capability of parylene HT®, it is also feasible to have the electret on the rotors, which is made of either a piece of metal or an insulator. The maximum power output, 17.98 µW, is obtained at 50 Hz with an external load of 80 MΩ. For low frequencies, the generator can harvest 7.7 µW at 10 Hz and 8.23 µW at 20 Hz