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T. Tokuda, R. Asano, K. Hiyama, Y. Terasawa, Y. Tano, J. Ohta; A Microelectronics-Based Flexible Retinal Stimulator for Retinal Prosthesis With an Improved Safety and Fault Tolerance. Invest. Ophthalmol. Vis. Sci. 2008;49(13):1783.
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© ARVO (1962-2015); The Authors (2016-present)
We have developed a high-density, flexible retinal stimulator based on microelectronics technology. In this work, for the sake of safety for retinal tissue and fault-tolerance of the device functionality, we implemented a novel operating scheme on the device architecture.
The stimulator is designed with multi-chip architecture. Small-sized (600 µm sq.) LSI (large scale integration) stimulators named "unit chip" are assembled on a flexible substrate and bulk Pt electrodes are formed on the stimulator. The flexible stimulator is a single-site stimulator with addressable Pt electrodes distributed on unit chips aligned on the flexible substrate. We can operate the flexible stimulator with only four input lines named; VDD, GND, CONT, and STIM. Any one of the Pt electrodes on the multi-chip stimulator can be selected and connected to the STIM input line for retinal stimulation. We have successfully performed retinal stimulation on rabbits as reported in ARVO2007. Since unit chip has no monolithic stimulation generator, very small electricity is consumed in the stimulation phase. We designed a new unit chip with an idea of "pulsed-powering" operating scheme, in which we supply electricity only in the control (electrode selection) phase, and cut it in the stimulation phase.
In the pulsed-powering operation, the time in which DC voltage is applied between VDD and GND lines will be reduced as short as 1% of the total operation time, even in the worst case.
The presented device architecture greatly improves the safety for retinal tissue, even in the case the stimulator is broken and electricity leakage occurs. We describe the device circuitry and demonstrate the proposed operating scheme in detail, based on both simulation, and experiments.
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