BCI Micro-sensory System Based On CMOS Integrated Circuit Technology

Brain-Computer interfaces(BCI) provide a direct communication and control channel for sending messages and instructions. Using the non-neuromuscular channel, BCIs read electrical signals or other manifestations of brain activity and translate them into a digital form that computers or other electrical devices can understand, process, and convert into actions of some kind, such as moving a cursor or turning on a TV. BCI technology is an interdisciplinary technology integrating neurology, engineering, micromachining, math, computer science and more other relevant techniques.Neural microelectrodes are the most important part of a BCI system providing necessary tools to decode thinking process of the brain. Based on the development of CMOS and MEMS technology, this paper discusses a new type of implantable neural microelectrodes with 3-D structure and two-ways communications. This neural microelectrodes system can not only record from multi-activity of neurons but cure some disease like Poliomyelitis, Parkinson, Deaf and Epilepsy by sending stimulate signal to nervous system. The design of the microelectrodes system involves the following parts: Research of the neural signal and recording model; Design of materials, structure and manufacture of the microelectrodes; Design of front-end neural signal recording and conditioning ASIC; Research of integrate techniques of microelectrodes and ASIC. And in-vivo experiments, which took SD guinea pigs as subjects, have also been done to test the correctness and stability of the whole system.Besides, the design and fabrication of front-end neural signal recording and conditioning ASIC is given by this paper in details. Based on CMOS 0.35 um technology and standard design flow, integrated analog circuits including cascaded close-loop operational amplifier, high-pass filter and biasing circuit are designed. Also, integrated digital circuits like multiplexer, mode selecting circuit and time-divided MUX are developed to meet the need of multi-channel recording. All the design processes are simulated by HSPICE and the simulation results are proved correct. And layout of the ASIC passes DRC and LVS testing successfully. After the ASIC is fabricated, it is packaged by bonding machine onto specially developed testing PCB. In-vitro experiments have been done both in recording and stimulating mode.