Mechanical Engineering ETDs

Publication Date

Fall 12-16-2023

Abstract

This study presents a flexible sensor/harvester device to be used in both electromagnetic sensing and energy harvesting applications for smart grids. When a current passes through a wire, the sensor detects the magnetic field created by that current. The sensor magnet interacts with the wire magnetic field resulting in a transfer of energy through the piezoelectric cantilever. Piezoelectric, conductive, magnetic, and magnetostrictive composite thin films were prepared to fabricate this device.

Initially, the magnet of the cantilever was optimized considering its shape, thickness, length, taper angle etc. via both simulations and experiments. Peak to peak voltage versus cantilever position graph was drawn for several different magnets. The triangular shape showed the widest sensing range around 18 mm. Experiments have been verified by COMSOL Multi physics software simulations constructing the magnetic flux density-position graphs. After the geometry optimization of the magnet, numerous 0-3 composite thin films were fabricated using piezoelectric, conductive, magnetic, and magnetostrictive powder in different polymers for comparison. After blending the materials, the spin coating method was used with various spin speeds to obtain different film thicknesses. Mainly, lead zirconate titanate (PZT), silver (Ag), neodymium (NdFeB), and Terfenol-D particles were used to create these functional films. After demonstrating that the functional thin films fabricated in this research can be successfully used to fabricate multilayered devices such as a micro-scale capacitor or a thin film energy harvester, thin film sensor/harvester versions of the bulk devices were fabricated and tested successfully. The broadest sensitivity region was obtained again from the piezoelectric thin film that has triangular thin film magnet positioned in such a way that its tip faces the free end of the cantilever. 40 wt.% concentration Ag-PI composites were used as electrodes.

Finally, magnetostrictive thin films having various ball-milled Terfenol-D particle concentrations were fabricated to be used as a single layer sensor instead of using multiple layers of thin films. The thin film sensors were tested using a Helmholtz coil and their response were determined in terms of tip deflection and current gained.

Keywords

piezoelectric, magnetostrictive, conductive, thin film, sensor, harvester

Degree Name

Mechanical Engineering

Level of Degree

Doctoral

Department Name

Mechanical Engineering

First Committee Member (Chair)

Nathan Jackson

Second Committee Member

Yu-Lin Shen

Third Committee Member

Matthias Pleil

Fourth Committee Member

Ali Bidram

Document Type

Dissertation

Language

English

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