Liquid-encapsulated energy harvester for low frequency vibrations

This paper presents the design, fabrication, and testing of prototype liquid-encapsulated energy harvester (LEEH) using PVDF electrets. Unlike harvesters reported in previous literature, this LEEH uses flowing liquid rather than resonating structures to induce variable capacitance, thus is more suitable for low frequency vibration energy harvesting. Manufactured prototypes with three different types of liquid (N-methyl-2-pyrrolidone, N, N-Dimethylformamide, and glycerin) are tested in horizontal vibration (@10Hz) and rotary motion (@2r/min) mode, respectively. It is shown that LEEH injected with DMF, which is of higher permittivity and lower viscosity, is of better performance in both horizontal vibration and rotary motion testing. With 90μL DMF dose, maximum output voltage of 470mV is obtained on 5.5MΩ resistance load @2mm, 10Hz horizontal vibration.