Development of an optoelectronic neural stimulator using a photovoltaic cell integrated with a light emitting diode for in-vivo optogenetics

Abstract

Neural stimulation by light in optogenetics present a new approach to stimulate targeted neuron compared to electrical stimulation that affects another cell. This paper indicates the development of a wireless implantable optoelectronic neural stimulator for optogenetic research using photovoltaic (PV) cells and light emitting diodes (LEDs). The micro LED was used to stimulate the photo-responsible cells and the PV was coupled together to turn on the LED. The GaAs-based PV device is designed near infrared light with high tissue penetration, and it is made of a tandem structure composed of three layers with optimized height to increase the absorption rate of light. Using the standard micro-electronic fabrication process, the PV and the LED were made and bonded. The stimulator was designed in the shape of a micro-sized cube with 400 μm sides. It is small enough to be implanted in the brain and also possible for deep brain stimulation. In this experiment, we demonstrated that PV can generate enough energy to turn on the LED with high efficiency of 34 %. And we show that the emitted light of the stimulator can stimulate the HEK cell using patch clamp set-up. Therefore, the induced photocurrents by our stimulator would be sufficient enough to evoke neuronal firing if our stimulator was implanted in the mammalian brain.