Implantable Optoelectronic Devices for Observation and Control of Biological Functions

We have developed implantable optoelectronic devices based on microelectronics technology for measuring and controlling biological functions. Electrical stimulation and measurement are established to effectively control and measure biological functions and are widely used in medical applications such as artificial retina, deep brain stimulation, and brain-machine interface. Recently, optogenetics, a rapidly developing optical method based on genetic engineering, enables light-mediated communication with neurons, providing powerful neuroscience and life-science tools. For example, ChR2 is a photo-sensitive ion channel and can optically control specific neural cell activities. GCaMP is a Ca ion sensor with green fluorescence protein and can optically observe specific neural cell activities. These proteins can be easily expressed in specific neural cells with gene transfection using virus infection. Based on these technologies, the development of implantable optoelectronic biomedical devices that use electrons and photons to measure and control biological functions in vivo is gaining momentum. Firstly, micro-imaging devices that can be directly implanted in a mouse brain are introduced. The device can be used to observe neural activities through fluorescence and is applied to observe mice's addiction and pain phenomena. The implantable micro-imaging devices have features of lightweight and wide filed-of-view. In addition, two devices can be implanted simultaneously, and thus they can observe the network activities in the mouse brain. Secondly, optical stimulation devices with micro-LED arrays are introduced. They are used to identify the dopamine pathway in the monkey brain. The LED array can be achieved to cover a large area to be optically stimulated. Finally, challenges and prospects for the devices are discussed.