Fabrication, characterization and modelling of electrostatic micro-generators

Abstract

This paper presents an electrostatic energy-harvesting device for electrical energy extraction from vibrations. We successfully fabricated prototypes of completely packaged micro-generators with a chip size of 5 mm by 6 mm. This was achieved using a modified SOI technology developed for inertial sensors at HSG-IMIT. Micro-generators produce a maximum rms power of 3.5 μW when they are excited at their resonance frequency with an input excitation of 13 g. During a long-term experiment over a period of 2 h, the electrostatic energy harvester generated a total net energy of 13.38 mJ corresponding to an average power of 1.58 μW. The effect of mechanical stoppers and the bias voltage on the generated power is also evaluated. In order to get a more profound understanding of the dynamic behaviour of the micro-generator, we have developed a signal-flow model for numerical simulation of the electrostatic transducer on system level. This model includes a mechanical and an electrical domain which are coupled by electrostatic forces. The limited displacement of the proof mass is also considered using an elastic stopper model. We show that the numerical model is capable of providing good predictions of the device behaviour.

Microscale Energy Harvesters with Nonlinearities Due to Internal Impacts

“…Even though this behavior can be exploited to extend device bandwidth, operating a conventional harvester in this regime has the considerable disadvantage that the output power saturates at high excitation levels and therefore the effectiveness of the device decreases. This saturation is quite generic and has been reported for a variety of devices [15][16][17][18][19][20].…”

“…These effects have been observed in several devices, e.g. in a mesoscale electromagnetic harvester by [16], a mesoscale piezoelectric harvester [18][19] and a microscale electrostatic harvester [17]. Some examples of measured and simulated characteristics of a microscale electrostatic energy harvester from [30] are shown in Figure 2 which displays "clipping" of the response and extended up-sweep bandwidth, and Figure 3 which displays saturation.…”

“…Microscale energy harvesters have typical effectiveness in the range from 1% to 10% and it is lower for smaller displacement limits [1]. The impact devices therefore achieve effectiveness values under displacement-limited operation that are comparable, or even favourable, in comparison with other device prototypes in [9,15,[17][18][33][34][35][36] with the same scale of the displacement limit. Together these examples show that there is much to be gained from transducing end-stops.…”

Impact-Based Electromagnetic Energy Harvester with High Output Voltage under Low-Level Excitations

“…The electromagnetic, piezoelectric, or electrostatic transduction mechanisms have been used by VEHs to convert mechanical energy into electricity [17][18][19][20][21][22][23][24]. The advantages of EMVEHs, such as high power density and high reliability, make them attractive in real applications.…”

High Energy Density Capacitance Microgenerators

“…This type of generators is used in many electrostatic MEMS generators [1,12,[18][19][20][21][22][23]. Their specific power is low not exceeding 1-10 μW/cm 2 because of high value of minimum interelectrode gap at low η.…”