Improvement of energy conversion effectiveness and maximum output power of electrostatic induction-type MEMS energy harvesters by using symmetric comb-electrode structures

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We introduce symmetric comb-electrode structures for the electrostatic vibrational MEMS energy harvester to lower the electrostatic constraint force attributed to the built-in electret potential, thereby allowing the harvester device to operate in a small acceleration range of 0.05 g or lower (1 g = 9.8 m s −2 ). Given the same device structure, two different potentials for the electret are tested to experimentally confirm that the output induction current is enhanced 4.2 times by increasing the electret potential from −60 V to −250 V. At the same time, the harvester effectiveness has been improved to as high as 93%. The device is used to swiftly charge a 470 µ F storage capacitor to 3.3 V in 120 s from small sinusoidal vibrations of 0.6 g at 124 Hz.