Nonlinear behaviour of membrane type electromagnetic energy harvester under harmonic and random vibrations

In this paper, the fabrication and characterization of a vibration-based polydimethylsiloxane (PDMS) membrane type electromagnetic energy harvester (EMEH) is reported. The harvester is suitable for generating electric energy from low level sinusoidal and narrow band random vibrations. Under acceleration levels greater than 0.1 g the behaviour of the EMEH is nonlinear, exhibiting sharp jump and hysteresis phenomena during frequency sweeps. Under sinusoidal excitations (0.1–3 g), the device produces a maximum of 88.8 mV load voltage and 39.4 μW power. At a matching load impedance of 10.1 Ω and when excited at its resonant frequency of 108.4 Hz and 3 g base acceleration, it generates a power of 68.0 μW, which corresponds to a power density of 30.22 μW/cm³. The nonlinear behaviour of the EMEH is exploited to harvest energy under narrow band random excitations. At higher acceleration levels of narrow band (50–150 Hz) random excitations, the device exhibits a broadening of the load voltage spectrum in comparison to the response under relatively low acceleration levels of narrow band (5–150 Hz) random excitations. The results show that the nonlinear behaviour of the PDMS membrane can be utilized to enhance the bandwidth of the harvester under narrow band random excitations and provides a simple alternative to other bandwidth broadening methods such as beam prestress, resonance tuning, or stopper impacts.