Mechanical Engineering ETDs

Publication Date

2-1-2012

Abstract

Electromagnetic metamaterials have demonstrated unique and unprecedented behaviors in a laboratory setting. They achieve these novel properties by utilizing geometry and structure, as opposed to a strict reliance on chemical composition, to dictate their interactions with electromagnetic (EM) radiation. As such, metamaterials significantly expand the toolkit from which engineers can draw when designing devices that interact with EM waves. However, the flexibility afforded by these structures also implies environmental sensitivities not seen in traditional material systems. Some recent efforts have borne this out, demonstrating significant strain- and temperature-dependence in metamaterial samples. To date, little has been done to fundamentally understand the mechanisms driving these dependencies. This understanding is crucial for developing engineering-quality predictions of the EM performance of metamaterial structures in a relevant environment, a crucial step in transitioning this technology from laboratory novelty to fielded capability. This study leverages equivalent circuit models to understand and predict the strain- and temperature-dependent EM properties of metamaterial structures. Straightforward analytic expressions for the equivalent circuit parameters (resistance, inductance, capacitance) detail the strain-induced changes in geometry as well as the temperature-dependence of the metamaterials constituent materials. These expressions are initially utilized to predict the strain-dependent shift in resonant frequency, a key descriptor of the metamaterial's EM behavior. These same expressions are then utilized to describe the metamaterial's strain- and temperature-dependent EM constitutive properties (permittivity, ε, and permeability, μ), which are critical for solving Maxwell's equations and performing EM simulations within the material. This study focused on the Electric-LC (ELC) resonator, a design commonly used to provide a tailored response to the electric field of the EM wave. However, the author believes that the same process, and similar analytic expressions for the circuit parameters and constitutive properties, could be used to successfully predict the strain- and temperature-dependence of other metamaterial structures, to include Split-Ring-Resonators (SRRs), a design commonly used to provide a tailored magnetic response to EM waves.'

Keywords

Metamaterials--Electromechanical analogies, Electric resonators.

Degree Name

Mechanical Engineering

Level of Degree

Doctoral

Department Name

Mechanical Engineering

First Committee Member (Chair)

Smith, David

Second Committee Member

Shen, Yu-Lin

Third Committee Member

Welsh, Jeffry

Sponsors

Air Force Office of Scientific Research

Document Type

Dissertation

Language

English

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