Advancing retinal prostheses from two to three dimensions
Abstract/Contents
- Abstract
- Advanced age-related macular degeneration (AMD) results in loss of central vision due to the gradual demise of photoreceptors. Currently, no therapy exists for such condition, and the loss of sight is permanent. Subretinal prostheses aim to restore sight via electrical stimulation of the surviving secondary neurons in the retina. This is a rapidly expanding area of research, especially with the boom of neural interfaces in recent years, with many groups focusing on various aspects of such devices. Our group is pursuing a full-system approach, from fabrication of the devices to in-vivo testing and to clinical trials. In our system, silicon photovoltaic pixels convert light into electrical current to stimulate the nearby neurons. Clinical trial of the first version of such implants having 100 µm pixels confirmed safety and feasibility of this approach and demonstrated prosthetic acuity closely matching the sampling limit of such arrays (20/420). Further improvement of visual acuity requires miniaturization of the pixels and faces many challenges. Simply scaling the pixel size down with flat bipolar arrays decreases the penetration depth of the electric field into the tissue, increasing the stimulation threshold beyond the capacity of even the best charge-injection material. To enable smaller pixels, moving from flat electrodes into a three-dimensional configuration helps mitigate these issues. Additionally, with planar junction diodes isolated by deep reactive ion etched (DRIE) trenches, carrier recombination at the pixel side walls may limit the light-to-current efficiency, and growing side-wall oxide results in oxidation-related stress in the Si, especially as pixels scale down. We addressed these limitations by transitioning from planar to vertical junction diodes. In this thesis, I will discuss the limitations on reducing the pixel size and overcoming these limitations by using (1) pillar electrodes, (2) honeycomb electrodes, and (3) vertical junction diodes validated ex-vivo and in-vivo. I present the design and fabrication processes of such devices and also demonstrate the resulting photodiode functionality, electrode performance, retinal integration with 3-D devices in-vivo and electrophysiological responses. This work will enable prostheses with pixels down to 20 µm, which corresponds to visual acuity exceeding 20/100. I conclude by discussing the remaining work toward full utilization of such devices and moving toward single-cell resolution.
Description
| Type of resource | text |
|---|---|
| Form | electronic resource; remote; computer; online resource |
| Extent | 1 online resource. |
| Place | California |
| Place | [Stanford, California] |
| Publisher | [Stanford University] |
| Copyright date | 2021; ©2021 |
| Publication date | 2021; 2021 |
| Issuance | monographic |
| Language | English |
Creators/Contributors
| Author | Huang, Tiffany Wanshing |
|---|---|
| Degree supervisor | Palanker, Daniel |
| Thesis advisor | Palanker, Daniel |
| Thesis advisor | Harris, J. S. (James Stewart), 1942- |
| Thesis advisor | Kamins, Theodore I |
| Degree committee member | Harris, J. S. (James Stewart), 1942- |
| Degree committee member | Kamins, Theodore I |
| Associated with | Stanford University, Department of Electrical Engineering |
Subjects
| Genre | Theses |
|---|---|
| Genre | Text |
Bibliographic information
| Statement of responsibility | Tiffany Wanshing Huang. |
|---|---|
| Note | Submitted to the Department of Electrical Engineering. |
| Thesis | Thesis Ph.D. Stanford University 2021. |
| Location | https://purl.stanford.edu/ks530xs2718 |
Access conditions
- Copyright
- © 2021 by Tiffany Wanshing Huang
- License
- This work is licensed under a Creative Commons Attribution Non Commercial 3.0 Unported license (CC BY-NC).
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