Date of Award

2-26-2009

Document Type

Thesis

Degree Name

Master of Science in Electrical Engineering

Department

Department of Electrical and Computer Engineering

First Advisor

LaVern A. Starman, PhD

Abstract

This thesis investigated the potential power output of a micro-electromagnetic generator fabricated using typical microfabrication materials and techniques. The design was based on a desire to free bio-implanted or remote electronic devices from batteries and their finite power supplies. A micro-electromagnetic generator could harvest energy from the ambient environment and power such devices indefinitely. Designs for the stator coil and rotor magnet components of the generator were optimized to produce maximum current density based upon electromagnetic theory. The relative orientation of the coil to the rotor and material selection for each component were considered. Coils were fabricated using low-resistance gold. A method for overlaying two evaporated gold wires was devised and successfully fabricated in order to avoid side-wall thinning of the coils which has been shown to lead to high resistivities. Rotors were made with nickel, a ferromagnetic material. The required parameters for reduced stress plating using a nickel electroplating bath were investigated in order to pattern and deposit nickel for the rotors. Once fabricated, the rotors were magnetized through the use of an electromagnet. In addition, a testing apparatus that provided precise alignment, a method of rotation to simulate operational functionality, and power measurement capabilities was designed and assembled. Testing of the magnets showed that the nickel rotors were able to be highly magnetized when placed near a strong field. However, upon removal from the field the magnetization quickly dissipated. It was determined that the coercivity, or magnetic hardness, of electroplated nickel was too low for the rotor magnets to retain a field for any appreciable amount of time. Testing of the micro-generator revealed that power output did not exceed 2 nA, which was expected given that the magnetic rotors did not retain their flux density. It was shown that nickel does not maintain the flux density required for a micro-electromagnetic generator and different materials should be investigated.

AFIT Designator

AFIT-GE-ENG-09-42

DTIC Accession Number

ADA499005

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