Ph.d. forsvar Pratik Kusumanchi

Principal supervisor: Professor Stephan Sylvest Keller
Co-supervisor:  Assistant Professor Rasmus Schmidt Davidsen

Examiners:
Associate Professor Andrea Crovetto, DTU Nanolab
Professor Massimo De Vittorio, IIT Lecce.
Professor Maria Tenje, Uppsala University

Chairperson at defense:
Professor Rafael Taboryski

Abstract:

Retinal diseases such as age-related macular degeneration (AMD) and retinitis pigmentosa (RP) cause blindness in millions of people worldwide by damaging the eye’s photoreceptor cells, which are crucial for vision. With limited treatment options, retinal implants offer a promising solution by bypassing these damaged cells and directly stimulating the remaining healthy retinal cells to restore some sight. These

implants work by capturing light, converting it into electrical signals, and sending those signals to the brain to recreate images. They are typically placed in one of three locations in the eye: under the retina (subretinal), on top of the retina (epiretinal), or between the retina and the eye wall (suprachoroidal), with subretinal implants showing significant promise for AMD and RP patients.

Recent research has focused on enhancing retinal implants by miniaturizing their pixels and incorporating 3D microelectrodes, which improve the implant’s ability to stimulate remaining retinal cells. This thesis explores the use of pyrolytic carbon (PyrC), a novel material for electrodes in retinal implants, known for its excellent biocompatibility and electrical properties. Unlike traditional metals, PyrC can be fabricated into complex 3D structures, potentially offering better performance for neural interfaces.

The main goal of this thesis was to develop advanced cleanroom fabrication techniques to create 3D PyrC electrodes and integrate them into state-of-the-art p-n junction solar cells, forming miniaturized pixels for retinal implants. The research involved testing these 3D electrodes using porcine and rat retinas to evaluate their effectiveness in stimulating retinal cells compared to traditional 2D electrodes.

The study found that the 3D PyrC electrodes could stimulate retinal cells at lower voltages, outperforming the conventional 2D designs, which is crucial for reducing the power requirements of retinal implants.