Access Type

Open Access Dissertation

Date of Award

January 2012

Degree Type

Dissertation

Degree Name

Ph.D.

Department

Electrical and Computer Engineering

First Advisor

Yong Xu

Abstract

Epilepsy is a chronic disease characterized by recurrent, unprovoked seizures, where seizures are described as storms of uncontrollable neuro-electrical activity within the brain. Seizures are therefore identified by observation of electrical spiking observed through electrical contacts (electrodes) placed on the scalp or the cortex above the epileptic regions. Current epilepsy research is identifying several specific molecular markers that appear at specific layers of the epilepsy-affected cortex. However, technology is limited in allowing for live observation of electrical spiking across these layers. The underlying hypothesis of this project is that electrical interictal activity is generated in a layer- and lateral-specific pattern.

This work reports a novel neural probe technology for the manufacturing of 3D arrays of electrodes with integrated microchannels. This new technology is based on a silicon island structure and a simple folding procedure. This method simplifies the assembly or packaging process of 3D neural probes, leading to higher yield and lower cost. Various types of 3D arrays of electrodes, including acute and chronic devices, have been successfully developed. Microchannels have been successfully integrated into the 3D neural probes via isotropic XeF2 gas phase etching and a parylene resealing process.

This work describes in detail the development of neural devices targeted towards the study of layer-specific interictal discharges in an animal model of epilepsy. Devices were designed utilizing parameters derived from the rat model of epilepsy. The progression of device design is described from 1st prototype to final chronic device. The fabrication process and potential pitfall are described in detail. Devices have been characterized by SEM (scanning electron microscope) imaging, optical imaging, various types of impedance analysis, and AFM (atomic force microscopy) characterization of the electrode surface. Flow characteristics of the microchannels were also analyzed. Various animal tests have been carried out to demonstrate the recording functionality of the probes, preliminary biocompatibility studies, and the reliability of the final chronic device package. These devices are expected to be of great use to the study of epilepsy as well as various other neurological diseases.

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