Photovoltaic pixels for neural stimulation: circuit models and performance

David Boinagrov, Xin Lei, Georges Goetz, Theodore I. Kamins, Keith Mathieson, Ludwig Galambos, James S. Harris, Daniel Palanker

Research output: Contribution to journalArticle

27 Citations (Scopus)
199 Downloads (Pure)

Abstract

Photovoltaic conversion of pulsed light into pulsed electric current enables optically-activated neural stimulation with miniature wireless implants. In photovoltaic retinal prostheses, patterns of near-infrared light projected from video goggles onto subretinal arrays of photovoltaic pixels are converted into patterns of current to stimulate the inner retinal neurons. We describe a model of these devices and evaluate the performance of photovoltaic circuits, including the electrode-electrolyte interface. Characteristics of the electrodes measured in saline with various voltages, pulse durations, and polarities were modeled as voltage-dependent capacitances and Faradaic resistances. The resulting mathematical model of the circuit yielded dynamics of the electric current generated by the photovoltaic pixels illuminated by pulsed light. Voltages measured in saline with a pipette electrode above the pixel closely matched results of the model. Using the circuit model, our pixel design was optimized for maximum charge injection under various lighting conditions and for different stimulation thresholds. To speed discharge of the electrodes between the pulses of light, a shunt resistor was introduced and optimized for high frequency stimulation.

Original languageEnglish
Pages (from-to)85-97
Number of pages13
JournalIEEE Transactions on Biomedical Circuits and Systems
Volume10
Issue number1
Early online date23 Jan 2015
DOIs
Publication statusPublished - 29 Feb 2016

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Keywords

  • neural stimulation
  • optical stimulation
  • photovoltaic arrays
  • retinal prostheses

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