Microelectrode array with integrated nanowire FET switches for high-resolution retinal prosthetic systems

Abstract

In this paper, a novel microelectrode array integrated with nanowire field-effect transistor (FET) switches is developed for retinal prosthetic systems. Retinal prosthetic systems require many electrodes (generally more than several hundreds) and this paper presents a novel method of integrating silicon nanowire-FET switches with microelectrodes that can significantly reduce wiring complexity. Also, in order to fit the curvature of an eyeball, the silicon nanowire FETs are transferred to a flexible substrate. In order to demonstrate the concept of using FETs for switching collocated retinal microelectrodes, a microelectrode array with 32 × 32 pixels is fabricated, which has 1,024 microelectrodes. Using the FET switches in a two-dimensional array addressing configuration, 1,024 microelectrodes are addressed by only 64 lines (32 for scan and 32 for data), as compared to requiring 1,024 lines in the conventional one-to-one configuration. With the gate voltage of −5 V, the threshold voltage, current on/off ratio, and on-resistance of the fabricated silicon nanowire-FET switch are −0.4 V, 1 × 107, and 37–47 kΩ, respectively. The maximum allowable current injection limit of the silicon nanowire-FET switch integrated microelectrode is 44 μA with a pulse duration of 1 ms. These results show an excellent potential for high-resolution retinal prosthetic systems.

Application of Nanowires for Retinal Regeneration

“…Silicon nanowires coated with gold were shown to be more effective at the simulation of photoreceptors; this is mostly attributed to the higher surface to the area for sensing light and charge transfer [61,62]. Another type of nanostructures is thin films functionalized with the nanoparticle to sense light.…”

Contactless Liquid Sensing Technique Using a Quartz Oscillator

“…In the case of high-resolution retinal prosthesis systems that use external cameras, the electrical interface becomes complicated mainly because of the wiring complexity. (38) Therefore, many commercialized retinal prostheses that use an external camera, such as the Argus II system (Second Sight Medical Products Inc., United States) (39) or EpiRet3 (EpiRet GmbH, Germany), (40) are implemented with a small number of channels. On the other hand, retinal prosthetic devices with embedded photodetectors for image perception, such as the 'artificial silicon retina' (US Optobionics, United States) (41) or Alpha IMS (German Retina Implant AG, Germany), (12) have a relatively large number of channels owing to the collocation of the photodetector, stimulation circuit, and electrodes in a single channel.…”

“…(42)(43)(44) In our previous reports, a novel retinal stimulation device integrated with silicon nanowire (SiNW)-based field-effect transistor (FET) switches and photodetectors was demonstrated. (38,(45)(46)(47)(48)(49) The SiNWs are fabricated by a top-down method for wafer-level transfer on a flexible substrate, which can achieve very thin MEAs without compromising device flexibility. As shown in Fig.…”

Neuron Stimulation Device Integrated with Silicon Nanowire-Based Photodetection Circuit on a Flexible Substrate

“…A key to successfully developing high-resolution systems is that the stimulation signals generated from image information are individually transmitted to a large number of stimulating electrodes [19]. In the case of retinal prosthesis systems that use external cameras, such an electrical interface becomes very complicated and difficult to implement because a camera and MEA are physically distinct and separate from each other.…”

“…The SiNW-based photodetection circuit comprises a voltage divider and a current driver that uses a SiNW PD [22], SiNW FETs [19], and micro electrodes. The SiNW FET and the SiNW PD are connected in series via the voltage divider, making a large resistance variation in the SiNW PD desirable because the output voltage changes when the resistance varies when light detection occurs.…”