Examination Committee

Prof Hoi Sing KWOK, ECE/HKUST (Chairperson)
Prof Amine BERMAK, ECE/HKUST (Thesis Supervisor)
Prof Leanne L H CHAN, EE/CityU (HK) (Thesis Co-supervisor)
Prof Zhi Yong FAN, ECE/HKUST

Abstract (revised)

Retinal degeneration diseases, like retinitis pigmentosa (RP) and age-related macular degeneration (AMD), cause gradual lose of sight. In such diseases, the optic nerve and ganglion cells are healthy and functional, only a small part of the retina is damaged. In order to restore vision, retinal prosthesis system is used to stimulate the ganglion cells and subsequently visual signals are transmitted to the brain.

Currently, the electrode density is very low compared to the density of ganglion cells, and the restored vision is limited in resolution. The design and fabrication of high density electrodes is a very important research problem for high resolution sight recovery. When scaling down the electrodes to achieve higher density, stimulation efficiency is becoming increasingly important.

In this thesis, we explore the design and fabrication of carbon nanotube (CNT) electrodes to fulfil the above mentioned requirements. Carbon nanotube electrode pillars embedded in Parylene-C are designed to achieve stable protruding structure suitable for local stimulation. The results showed that, when synthesizing the electrode samples downward instead of upward, the impedance was decreased by 90 times, the double layer capacitance was increased by 55 times, the effective surface area was increased by 25 times, the water dipole thickness decreased by half, and interface resistance was decreased by 20 times, when compared to the previous art. The proposed Parylene-C embedding process further improves the adhesion between CNT electrodes and Titanium routing layer and hence enabling to lower the overall impedance. The thesis finally illustrates that high density CNT-based micro electrodes is feasible.