Energy Harvesting Through Reverse Electrowetting

Shrivastava, R (2014) Energy Harvesting Through Reverse Electrowetting. Masters thesis, Indian Institute of Technology, Hyderabad.

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Abstract

Over the last decade electrical batteries have emerged as a critical bottleneck for portable electronics development. High-power mechanical energy harvesting can potentially provide a valuable alternative to the use of batteries, but, until now, a suitable mechanical-to-electrical energy conversion technology did not exist. Here we describe a novel mechanical-to-electrical energy conversion method based on the reverse electrowetting phenomenon. Reverse electrowetting has emerged as a highly potential method for high power energy harvesting with good environmental coupling. Device simulation using fluid flow model of COMSOL multiphysics has been presented in this thesis. Harvested energy from this kind of device is directly proportional to change in capacitance from wetting to non-wetting condition i.e. the device should have high capacitance per unit volume. It has been found that high K dielectric material offers high capacitance at low operating voltage. Further reduction in operating voltage can be accomplished by decreasing dielectric thickness. However it has been proposed to use 10nm dielectric thickness for ease in fabrication. Finally capacitance of 4.213nF at an operating voltage of 4.9V has been achieved by choosing 10nm of TiO2 ( ) as a dielectric material with the device of radius 100um. Instead of using single big droplet, use of multiple small droplets of same volume offer more capacitance and hence the harvested energy. Apart from this simulation, device fabrication has been done using two different methods, one is based on UV lithography and another is based on X-ray lithography. All the obstacles and problems encountered in this fabrication have been discussed thoroughly in this thesis.

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