A power supply module for autonomous portable electronics: ultralow-frequency MEMS electrostatic kinetic energy harvester with a comb structure reducing air damping

Abstract

A MEMS electrostatic kinetic energy harvester (e-KEH) of about 1 cm 2 , working at ultralow frequency (1–20 Hz), without any supported additional mass on its mobile electrode, and working even without a vacuum environment is reported. The prototype is especially suitable for environments with abundant low frequency motions such as wearable electronics. The proposed e-KEH consists of a capacitor with a finger-teeth interdigited comb structure. This greatly reduces the air damping effect, and thus the capacitance variation remains important regardless of the presence of air. With the new design, the energy transduced per cycle of excitation is no less than 33 times higher than the classic design within 10–40 Hz/2 g peak , while is 85 times higher at 15 Hz/2 g peak . An enclosed miniature ball combined with non-linear stoppers enables the oscillation of the movable electrode through impact-based frequency up-conversion mechanism, which is also improved by the low air damping. Thanks to this new design, a higher efficiency than the classic gap-closing comb structure is obtained, as a larger range of working frequency (1–180 Hz) in air. A maximum energy conversion of 450 nJ/cycle is obtained with a bias voltage of 45 V and an acceleration of 11 Hz, 3 g peak . Working with a diode AC-DC rectifier, the proposed KEH is able to support up to 3 RFID communications within 16 s while operated at 11 Hz, 3 g peak .

Energy Solutions for Wearable Sensors: A Review

“…An electrostatic kinetic energy harvester is able to greatly reduce the size of kinetic energy harvesters, which is very competitive in wearable devices. Microelectromechanical System (MEMS) electrostatic energy harvesters produce capacitance variation by mechanical vibrations and are typically designed in comb format [ 98 ]. MEMS electrostatic energy harvesters consist of a central mass and attached parallel electrostatic transducers.…”

Spray-coated electret materials with enhanced stability in a harsh environment for an MEMS energy harvesting device

“…Electret materials have been used in various fields, such as pressure sensors, barometers and acoustic transducers in microphones [1][2][3][4][5] , thanks to the quasipermanent electric charge feature in electrets. Recently, electrets have been explored for use in new applications in MEMS vibration energy harvesters that are based on electrostatic induction [6][7][8][9][10][11][12] . A precharged electret can provide an electrostatic field between the static electrode and movable electrode for a long period of time.…”

Design and analysis of a vibration energy harvester using push-pull electrostatic conversion

“…At small scale (such as micro-electromechanical system, MEMS) applications, the electrostatic conversion is preferable over the electromagnetic and piezoelectric methods due to its high scalability and low-resistivity materials [4,11,17,24,[47][48][49]. These advantages resulted in the development of MEMS-based electrostatic EH devices [28,47,[50][51][52][53][54][55][56][57]. However, they have limitations including (1) high electrical impedances, (2) impact of parasitic capacitances, (3) need for alignment of electrets and electrodes with high accuracy, and (4) maintaining high charge density in the electret [6,10,19].…”

“…Given that most of the mechanical energy sources of vibration in the environment are available at low frequencies [52,58], vibration energy harvesters with a focus on low frequencies need more attention. Thus, in the past dacade, a considerable amount of literature has been published on electrostatic EH for low vibration frequency applications [26,39,43,52,57,58,60]. Such studies indicate a growing interest and value of low frequency devices.…”