THESIS
2013
xiii, 69 pages : illustrations ; 30 cm
Abstract
For decades, the recording and electrical stimulation of nerve cells employed in
neural prostheses (mainly auditory and motor prosthetics) has significantly improved
the lives of patients. However, only recently have several research groups had the
incentive to develop a retinal prosthesis to restore vision for the millions of blind and
partially sighted people who suffer from age-related macular degeneration (AMD) and
retinitis pigmentosa (RP). A number of experiments have demonstrated that vision
could be restored by communicating directly with retinal neurons. This can be achieved
through an array of implanted microelectrodes, which supply electrical stimulation
pulses at various locations on the retina.
However, current retinal implants provide just a few electrodes where...[
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For decades, the recording and electrical stimulation of nerve cells employed in
neural prostheses (mainly auditory and motor prosthetics) has significantly improved
the lives of patients. However, only recently have several research groups had the
incentive to develop a retinal prosthesis to restore vision for the millions of blind and
partially sighted people who suffer from age-related macular degeneration (AMD) and
retinitis pigmentosa (RP). A number of experiments have demonstrated that vision
could be restored by communicating directly with retinal neurons. This can be achieved
through an array of implanted microelectrodes, which supply electrical stimulation
pulses at various locations on the retina.
However, current retinal implants provide just a few electrodes whereas at least
several thousand of pixels are required for functional restoration of sight. As the area of
the retina targeted for electrical stimulation is less than 4 mm by 4 mm, an increase in the number of electrodes necessitates a decrease in their size and spacing. Such decrease
in size and spacing of electrodes presents multiple challenges that are addressed in this
research.
This thesis is concerned with the development of a novel high-density carbon
nanotube microelectrode array chip for use in an epiretinal prosthesis. Vertically aligned
carbon nanotubes (VACNT) were synthesized by microwave plasma-enhanced
chemical vapor deposition and thermal chemical vapor deposition and were
characterized by electrochemical experiments such as cyclic voltammetry, impedance
spectroscopy and potential transient measurements. Through-silicon vias (TSVs) were
fabricated and partially filled with polycrystalline silicon to allow electrical connection
from the electrodes to a stimulator microchip. In response to the demand for a higher
resolution retinal prosthesis, we have developed a unique process to obtain a
high-density electrode array by making the microelectrodes smaller in size and larger in
number.
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