Flat and robust out-of-plane vibrational electret energy harvester

Abstract

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.

Electret based vibration energy harvester for sensor network

“…On the other hand, when the amplitude is much smaller than the initial gap, ΔC diminishes. Chiu and Lee [23] and Takahashi et al [24] separately developed an out-of-plane electret generator having a similar structure. Advantage of this type of generators is that a plain electret layer can be used, by which issues for patterned electrets are avoided.…”

Electret Length Optimization of Output Power for Double-End Fixed Beam Out-of-Plane Electret-Based Vibration Energy Harvesters

“…Electret-based vibration energy harvesters (E-VEHs) can be divided into two types, in-plane [14][15][16] and out-of-plane [17][18][19][20][21], depending on the vibration direction. In-plane E-VEHs operate under vibration parallel to the electret surface, whereas out-of-plane E-VEHs do so under vibration normal to the electret surface.…”

“…For a double-ended fixed beam, the symmetry of the beam around the proof mass prevents any lateral and rotational motion of the proof mass other than its main translation motion and a greater capacitance variation can be obtained before the counter-electrode touches the electrode. Yi [18] presented two kinds of double-ended fixed beam out-of-plane E-VEHs fabricated using copper plates and a flexible printed circuit board, respectively. Asanuma [20] achieved a large capture bandwidth by optimizing the air gap with less output power loss for double-ended fixed beam out-of-plane E-VEHs.…”

A sandwich-structured MEMS electret power generator for multi-directional vibration energy harvesting

“…These features would limit the applicability of energy harvesters in practical scenarios. In order to address these issues, various designs and implementing methods have been proposed to achieve broadband or two-dimensional energy harvesting [4][5][6][7]. We previously proposed a rotational symmetrical resonant system that has a disk-shaped circular mass suspended by several sets of parallel-spiral springs around, which exhibits a good potential in the development of a three-dimensional electret-based energy harvesting device [5].…”