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In this work the design of a new epiretinal stimulator approach with integrated bendable imaging sensor is presented. First, the fundamental differences to the existing retinal stimulation implants is described. In the second part, a brief description of the novel designed implant is given, where several integrated circuits are placed on a single polyimide foil to create the mechanically flexible implant. Then the design of the developed dies is presented, containing the image sensor with a signal processing unit, a configurable waveform generator and a current controlled stimulation unit.

Retina degeneration is one of the leading causes of blindness nowadays and cannot be cured in most cases. It has been shown that electrical stimulation of retinal ganglion cells can generate visual perceptions and therefore implantable electrode arrays can be possible treatment for these patients. Most implants developed for that purpose use electrode arrays with a size of a few millimeters squared and therefore could restore only a very small field of vision and hardly improve orientation in an unknown environment. In this paper we present results of the development of an implantable electrode array covering about 100 mm(2) of retinal tissue.

Nowadays, implanted electrical stimulators are used for many clinical treatments such as deep brain stimulation or retinal stimulation. However, with the electrode-tissue interface impedance shaping, neuroscientists and clinicians are unable to truly verify stimulus waveform efficiency at stimulation targets vicinity. In this paper, we present a multi-application electrical stimulator architecture addressing this issue. This architecture purpose is to predict the stimulus shaping from mono/bipolar impedance spectra measurement and then to adapt the stimulus waveform generation. Since the impedance might change along the implant's life, the impedance measurement module must be embedded with the stimulator. At the end, we present specification requirements to achieve this stimulus adaptation irrespective of the therapeutic application.

A novel flexible neural interface device was proposed, designed and fabricated. The device realizes electrical stimulation and measurement of neural tissues using an array of smart electrodes. The smart electrode has intelligence by dedicated CMOS microchip. Thanks to the smart electrodes high functions of the array with large number of electrodes are obtained only with 4 wiring connected to external equipments. Moreover, the device has enough flexibility for low invasion to the living body tissues. As one of in vivo evaluations, retinal stimulation was performed with the device using an experimental animal. Stimulus function of the device implanted into the living body was demonstrated successfully, responses caused by the stimulation were observed.

A CMOS-based flexible retinal stimulator equipped with bullet-shaped bulk Pt electrodes was fabricated and demonstrated. We designed a new CMOS unit chip with an on-chip stimulator, single- and multi-site stimulation modes, and monitoring functions. We have developed a new structure and packaging process of flexible retinal stimulator with bullet-type bulk Pt electrode. We have confirmed the retinal stimulation functionality in an in vivo stimulation trial on rabbit's retina.

We developed a CMOS LSI stimulator chip for retinal prosthesis technology with features of (1) multi-site stimulation using an on-chip stimulator, (2) light-controlled (image-based) stimulation. The retinal stimulator was configured as an array of small-sized intelligent CMOS stimulators called a “unit chip.” We can set different conditions for each unit chip connected to a single set of 5-channel bus wiring and perform multi-site, constant-current biphasic retinal stimulation. We implemented simple binary light-sensing circuitry on the unit chip to realize image-based patterned stimulation on the retina. We verified that all the implemented functionalities correctly work and characterized the performance of the circuitry. A demonstration for image-based patterned current injection using radially aligned unit chips was also performed.

A CMOS-based multi-chip flexible retinal stimulator with light-sensing function was designed. The light sensing function is implemented for light-controlled retinal stimulation in subretinal configuration. The basic functionality and feasibility of the multi-chip flexible retinal stimulator was confirmed. A photo-activating operation with adjustable photosensitivity was successfully implemented on the retinal stimulator without any additional input line. We demonstrated and characterized the photosensing function.