Date of Graduation

Spring 2017

Document Type

Honors Research Project

Degree Name

Bachelor of Science

Major

Corrosion Engineering - Cooperative Education

Research Sponsor

Dr. Hongbo Cong

First Reader

Dr. Ed Evans

Second Reader

Dr. Robert S. Lillard

Abstract

In this work, we use electrochemical impedance spectroscopy (EIS) to observe the response of a single, photo-lithographically created, interdigital transducer (IDT) sensor, dimensions 6mm X 6 mm, with capacitive elements 70μm X 500 nm. The IDT was exposed to different wetting conditions, droplets of DI water, 0.1 M NaCl, and 0.6 M NaCl, in volumes of 0.1, 0.3, 1, and 5 μL. Deliquescence of solid NaCl salt particles in a dynamic-humidity (%RH Increasing, 33% to 85%) atmosphere is examined. Equivalent circuit fitting of impedance spectra suggests linear trends for the capacitive equivalent circuit element parameters and a decaying logarithmic trend for the resistive element, with respect to electrolyte concentration vs. area of wetting. The sensor development process includes a 1 by 5 proof-of-concept linear array, and the eventual goal of a 5 by 5 matrix array. The array sensor aims to (1) determine the overall fraction of wet surface area, and (2) distinguish between electrolytes of varying conductivity, in a 2-dimensional gradient across a surface.

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