Photovoltaic retinal prosthesis for restoring sight to the blind: implant design and fabrication

Lele Wang; Keith Mathieson; Theodore I. Kamins; James Loudin; Ludwig Galambos; James S. Harris; Daniel Palanker

doi:10.1117/12.909104

6 February 2012 Photovoltaic retinal prosthesis for restoring sight to the blind: implant design and fabrication

Lele Wang, Keith Mathieson, Theodore I. Kamins, James Loudin, Ludwig Galambos, James S. Harris, Daniel Palanker

Proceedings Volume 8248, Micromachining and Microfabrication Process Technology XVII; 824805 (2012) https://doi.org/10.1117/12.909104
Event: SPIE MOEMS-MEMS, 2012, San Francisco, California, United States

Abstract

We have designed and fabricated a silicon photodiode array for use as a subretinal prosthesis aimed at restoring sight to patients who lost photoreceptors due to retinal degeneration. The device operates in photovoltaic mode. Each pixel in the two-dimensional array independently converts pulsed infrared light into biphasic electric current to stimulate remaining retinal neurons without a wired power connection. To enhance the maximum voltage and charge injection levels, each pixel contains three photodiodes connected in series. An active and return electrode in each pixel ensure localized current flow and are sputter coated with iridium oxide to provide high charge injection. The fabrication process consists of eight mask layers and includes deep reactive ion etching, oxidation, and a polysilicon trench refill for in-pixel photodiode separation and isolation of adjacent pixels. Simulation of design parameters included TSUPREM4 computation of doping profiles for n⁺ and p⁺ doped regions and MATLAB computation of the anti-reflection coating layers thicknesses. The main process steps are illustrated in detail, and problems encountered are discussed. The IV characterization of the device shows that the dark reverse current is on the order of 10-100 pA-negligible compared to the stimulation current; the reverse breakdown voltage is higher than 20 V. The measured photo-responsivity per photodiode is about 0.33A/W at 880 nm.

Citation Download Citation

Lele Wang, Keith Mathieson, Theodore I. Kamins, James Loudin, Ludwig Galambos, James S. Harris, and Daniel Palanker "Photovoltaic retinal prosthesis for restoring sight to the blind: implant design and fabrication", Proc. SPIE 8248, Micromachining and Microfabrication Process Technology XVII, 824805 (6 February 2012); https://doi.org/10.1117/12.909104

ACCESS THE FULL ARTICLE

INSTITUTIONAL
Select your institution to access the SPIE Digital Library.

SELECT YOUR INSTITUTION

PERSONAL
Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.

PERSONAL SIGN IN

No SPIE Account? Create one

PURCHASE THIS CONTENT

SUBSCRIBE TO DIGITAL LIBRARY

50 downloads per 1-year subscription

Members: $195

Non-members: $335 ADD TO CART

25 downloads per 1 - year subscription

Members: $145

Non-members: $250 ADD TO CART

PURCHASE SINGLE ARTICLE

Includes PDF, HTML & Video, when available