This paper reports the design, fabrication and testing of two types of out-of-plane electret energy harvesters. Copper plates and flexible printed circuit board (FPCB) were used to fabricate the harvesters for a lower fabrication cost and a more robust structure. Several dielectric materials were investigated and SiO 2 /Si 3 N 4 double layers were found to have better charge stability. The measured surface potential and charge density of the SiO 2 /Si 3 N 4 electret were −400 V and 13.5 mC m −2 , respectively. It was found that charge stability could be improved by multiple corona charging cycles. Using SiO 2 /Si 3 N 4 as the electret material, the measured power output was 20.7 μW at 110 Hz for 2 G acceleration with a 50 M load for the copper harvester and 0.82 μW at 172 Hz for 2 G acceleration with a 30 M load for the FPCB harvester.
Due to recent advances in low-power VLSI design technology, it has become feasible to power portable or remote electronic devices by scavenging the ambient energy. The design, fabrication and measurement of a capacitive vibration-to-electricity energy converter are presented in this paper. With a device area constraint of 1 cm 2 and an auxiliary battery supply of 3.6 V, the device was designed to generate an output power of 31 μW with an output saturation voltage of 40 V. An external mass of 4 g was needed to adjust the device resonance to match the input vibration of 2.25 m s −2 at 120 Hz. Mechanical contact switches were integrated onto the device to provide accurate charge-discharge energy conversion timing. The device was fabricated in SOI (silicon-on-insulator) wafers by deep silicon etching technology. Parasitic capacitance was minimized by partial back side substrate removal. Resonant frequencies of the fabricated device with and without the external mass agreed with the expected values. Without the external mass, the measured ac output power was 1.2 μW with a load of 5 M at 1870 Hz. Detailed circuit modeling and ac output power measurement of the devices with the external mass attached are in progress.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.