Date of Award

Spring 2018

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Mechanical & Aerospace Engineering

Committee Director

Xiaoyu Zhang

Committee Member

Shizi Qian

Committee Member

Yan Peng

Abstract

A typical Kelvin water dropper is a device that can convert gravitational potential energy to a high voltage electrostatic. This device consists of two inductors, two collectors, tubes, and electrical connections. A Kelvin water dropper is able to generate extremely high voltage by separating ions using two positive feedback loops. A Kelvin water dropper provides a low cost solution for the applications in which high voltage is needed. In the present research, low cost Microfluidic Kelvin Water Droppers (MKWDs) were developed and built in house for electrowetting applications. Two MKWDs with different tube inner diameters (254 and 508 μm) were constructed to evaluate their appropriate power output for electrowetting. It was demonstrated that higher flow rate led to higher voltage generated, whereas the MKWD with larger tube diameters generated less voltage.

Thereafter, contact electrowetting using the homemade MKWD was studied. Electrowetting is a process used to manipulate deformation of liquid droplets on a dielectric surface using an external electric field. In contact electrowetting, the droplet is in contact with a working electrode that applies the voltage. The electric field in the present research was applied using the MKWD. It was demonstrated that contact electrowetting of water droplets can be controlled using the MKWD. Then, a computational model was built to simulate the contact electrowetting using the MKWD. The model was successfully validated by comparing the experimental and simulation results.

Finally, contactless electrowetting using the MKWD was investigated. As compared to contact electrowetting, the working electrode was separated from the water droplets. When applying an electric field using the MKWD, it was observed that the water droplet first corrugated due to electrostatic attraction, and then collapsed due to electrowetting. Unlike contact electrowetting, two processes were involved in contactless electrowetting. To simulate two processes, the first model was built based on the theory of electrostatics, and the second model was based on the conventional electrowetting. Both models were validated by a nice agreement between the experimental and simulation data.

ORCID

0000-0001-6807-6720

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