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Access Type

WSU Access

Date of Award

January 2016

Degree Type

Dissertation

Degree Name

Ph.D.

Department

Electrical and Computer Engineering

First Advisor

Ming-Cheng Cheng

Abstract

Electrical stimulation and recording of neural cells have been widely used in basic neuroscience studies, neural prostheses, and clinical therapies. Stable neural interfaces that effectively communicate with the nervous system via electrodes are of great significance. Recently, flexible neural interfaces that combine carbon nanotubes (CNTs) and soft polymer substrates have generated tremendous interests. CNT based microelectrode arrays (MEAs) have shown enhanced electrochemical properties compared to commonly used electrode materials such as tungsten, platinum or titanium nitride. On the other hand, the soft polymer substrate can overcome the mechanical mismatch between the traditional rigid electrodes (or silicon shank) and the soft tissues for chronic use. However, most fabrication techniques suffer from low CNT yield, bad adhesion, and limited controllability. In addition, the electrodes were covered by randomly distributed CNTs in most cases. In this study, a novel fabrication method combining XeF2 etching and parylene deposition was presented to integrate the high quality vertical CNTs grown at high temperature with the heat sensitive parylene substrate in a highly controllable manner. Lower stimulation threshold voltage and higher signal to noise ratio have been demonstrated using vertical CNTs bundles compared to a Pt electrode and other randomly distributed CNT films. Adhesion has also been greatly improved. The work has also been extended to develop cuff shaped electrode for peripheral nerve stimulation.

Fast scan cyclic voltammetry is an electrochemical detection technique suitable for in-vivo neurotransmitter detection because of the miniaturization, fast time response, good sensitivity and selectivity. Traditional single carbon fiber microelectrode has been limited to single detection for in-vivo application. Alternatively, pyrolyzed photoresist film (PPF) is a good candidate for this application as they are readily compatible with the microfabrication process for precise fabrication of microelectrode arrays. By the oxygen plasma treatment of photoresist prior to pyrolysis, we obtained carbon fiber arrays. Good sensitivity in dopamine detection by this carbon fiber arrays and improved adhesion have been demonstrated.

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