To harvest energy from human motion and generate power for the emerging wearable devices, energy harvesters are required to work at very low frequency. There are several studies based on energy harvesting through human gait, which can generate significant power. However, when wearing these kind of devices, additional effort may be required and the user may feel uncomfortable when moving. The energy harvester developed here is composed of a 10 μm PZT thin-film deposited on 50 μm thick stainless steel foil by the aerosol deposition method. The PZT layer and the stainless steel foil are both very thin, thus the patch is highly flexible. The patch can be attached on the skin to harvester power through human motions such as the expansion of the chest region while breathing. The energy harvester will first be tested with a moving stage for power output measurements. The energy density can be determined for different deformation ranges and frequencies. The fabrication processes and testing results will all be detailed in this paper.
This paper presents a system integration of micro-piezoelectric energy harvester (MPEH) system based on MPEHs fabricated with an aero-deposited PZT technique, including both the device and the interface circuit design. An in depth look at the deposition method known as aerosol deposition is analyzed. Secondly, various structural designs throughout the years will be introduced and discussed. Thirdly, the non-linear synchronized switching technique interfacing circuit was designed to boost the harvested power in comparison to standard rectifying circuits. The boosting effect in comparison to theoretical expectations will also be presented. The power dissipation effects of self-powered SSHI under low current has also been discussed. Experimental results show that the device based on silicon substrate showed a maximum output power of 21 μW with the output voltage of 2.2 Vrms, excited at 215 Hz under a 1.5 g vibrating source. In comparison, the device based on stainless steel substrate, driven under the same acceleration, had a maximum output power of 34 μW with 1.8 Vrms at the resonant frequency of 202 Hz. The power densities were 4.7 μW mm-2 and 7.6 μW mm-2 for the silicon substrate and the stainless steel substrate based devices, each. The cantilever structured MPEG was later improved to the power output of 200.28 μW. To further improve the output characteristic, the device was tested under vacuumed circumstance, which then gave the output power of 241.60μW, with a 6.02 Vrms under 1.5 g, 104.4Hz. The power boosting circuit gave a power gain of 2.03 times, as the overall system outputs 91.4 μW using the self-powered nonlinear technique under 0.75 g with a similar device. The overall system, using only the standard rectifying circuit was able to light a low consumption red- colored SMD-0805 packaged LED in a duty ratio of approximately 25%.