As blind patients with an intact optic nerve and damaged photoreceptor cells increase in number in recent years, there has been a growing interest in visual prostheses by electrically stimulating their retinas. Previous clinical studies indicated that blind patients perceive a controlled electrical current applied to a small area of the retina via electrodes as a spot of light. We propose a novel implantable device, so-called three-dimensionally (3D) stacked retinal prosthesis, which is composed of a photodetector, an image processor, electrical current generator circuits, and an electrode array on one chip. The spice simulation showed that our designed analog circuits for 3D stacked retinal prosthesis chip could output desirable electrical current with variable pulse width by controlling bias voltages.

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We have proposed a novel multilayer stacked retinal prosthesis chip based on three-dimensional integration technology. Implantable stimulus electrode arrays in polyimide flexible cables were fabricated for the electrical stimulation of the retina. To evaluate optimal retinal stimulus current, electrically evoked potential (EEP) was recorded in animal experiments using Japanese white rabbits. The EEP waveform was compared with visually evoked potential (VEP) waveform. The amplitude of the recorded EEP increased with stimulus current. The EEP waveform shows a similar behavior to the VEP waveform, indicating that the electrical stimulation of the retina can be exploited for the blind to perceive incident light to the retina.

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This paper presents a new calculation model of the switched reluctance motor (SRM) for use on SPICE which is a general-purpose circuit simulation program. In the calculation model, the electric circuit and magnetic circuit of SRM are separated and are coupled by proper controlled sources. Using the SPICE model, we can calculate readily and accurately the dynamic characteristics of the SRM.

A retinal prosthesis system with a three-dimensionally (3D) stacked LSI chip has been proposed. We fabricated a new implantable stimulus electrode array deposited with Platinum-black (Pt-b) on a polyimide-based flexible printed circuit (FPC) for the electrical stimulation of the retinal cells. Impedance measurement of the Pt-b electrode–electrolyte interface in a saline solution was performed and the Pt-b electrode realized a very low impedance. The power consumption at the electrode array when retinal cells were stimulated by a stimulus current was evaluated. The power consumption of the Pt-b stimulus electrode array was 91% lower than that of a previously fabricated Al stimulus electrode array due to a convexo-concave surface. In the cytotoxicity test (CT), we confirmed that Pt implantation induced no cellular degeneration of the rat retina. In the animal experiments, electrically evoked potential (EEP) was successfully recorded using Japanese white rabbits. These results indicate that electrical stimulation using the Pt-b stimulus electrode array can restore visual sensation.

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