Strathprints Home | Open Access | Browse | Search | User area | Copyright | Help | Library Home | SUPrimo

Photovoltaic retinal prosthesis : implant fabrication and performance

Wang, Lele and Mathieson, Keith and Kamins, Theodore I. and Loudin, James D. and Galambos, Ludwig and Goetz, Georges and Sher, Alexander and Mandel, Yossi and Huie, Philip and Lavinsky, Daniel and Harris, James S. and Palanker, Daniel V. (2012) Photovoltaic retinal prosthesis : implant fabrication and performance. Journal of Neural Engineering, 9 (4). ISSN 1741-2552

Full text not available in this repository. (Request a copy from the Strathclyde author)

Abstract

The objective of this work is to develop and test a photovoltaic retinal prosthesis for restoring sight to patients blinded by degenerative retinal diseases. A silicon photodiode array for subretinal stimulation has been fabricated by a silicon-integrated-circuit/MEMS process. Each pixel in the two-dimensional array contains three series-connected photodiodes, which photovoltaically convert pulsed near-infrared light into bi-phasic current to stimulate nearby retinal neurons without wired power connections. The device thickness is chosen to be 30 µm to absorb a significant portion of light while still being thin enough for subretinal implantation. Active and return electrodes confine current near each pixel and are sputter coated with iridium oxide to enhance charge injection levels and provide a stable neural interface. Pixels are separated by 5 µm wide trenches to electrically isolate them and to allow nutrient diffusion through the device. Three sizes of pixels (280, 140 and 70 µm) with active electrodes of 80, 40 and 20 µm diameter were fabricated. The turn-on voltages of the one-diode, two-series-connected diode and three-series-connected diode structures are approximately 0.6, 1.2 and 1.8 V, respectively. The measured photo-responsivity per diode at 880 nm wavelength is ~0.36 A W−1, at zero voltage bias and scales with the exposed silicon area. For all three pixel sizes, the reverse-bias dark current is sufficiently low (<100 pA) for our application. Pixels of all three sizes reliably elicit retinal responses at safe near-infrared light irradiances, with good acceptance of the photodiode array in the subretinal space. The fabricated device delivers efficient retinal stimulation at safe near-infrared light irradiances without any wired power connections, which greatly simplifies the implantation procedure. Presence of the return electrodes in each pixel helps to localize the current, and thereby improves resolution.

Item type: Article
ID code: 40461
Keywords: medical physics, biophysical techniques, biomaterials, Neuroscience. Biological psychiatry. Neuropsychiatry, Bioengineering, Biomedical Engineering, Cellular and Molecular Neuroscience
Subjects: Medicine > Internal medicine > Neuroscience. Biological psychiatry. Neuropsychiatry
Technology > Engineering (General). Civil engineering (General) > Bioengineering
Department: Faculty of Science > Institute of Photonics
Technology and Innovation Centre > Photonics
Related URLs:
    Depositing user: Pure Administrator
    Date Deposited: 18 Jul 2012 10:56
    Last modified: 28 Mar 2014 05:52
    URI: http://strathprints.strath.ac.uk/id/eprint/40461

    Actions (login required)

    View Item