Research On Key Technologies Of Fully-implanted Brain-computer-interface Microsystem

Fully-implanted brain-computer-interface is an emerging technology for long-term continuous recording or regulation of neural activity with high resolution,which will promote the application of implantable brain-computer-interface in neuroscience research and medical rehabilitation.The existing fully-implanted brain-computer-interface system realizes the miniaturization and full implantation through the combination of the integrated electrode,wireless power transfer and integrated circuit technology.However,the fully-implanted brain-computer-interface system is difficult to be effectively unified in terms of low power,small size and high performance.Therefore,the research on the key technologies of fully-implanted brain-computer-interface systems will help to improve the performance and promote the application in neuroscience research and medical rehabilitation.Aiming at the problems faced by the above fully-implanted brain-computer interface,this paper studies key technologies such as the front-end circuit structure of neural recording,the brain-computer interface system,and the wireless power transfer system.The specific work content is as follows:(1)A novel fully differential neural recording front-end structure is proposed,which can effectively reduce the noise of the implantable neural recording system.With the two operational amplifiers composed fully-differential structure,the external interference noise amplification is effectively suppressed.Through simulation and actual tests,the gain of the neural recording front-end circuit is 66 d B in the bandwidth range of 0.1 Hz-7.5 k Hz,and the noise level is less than 100n V/√Hz,which is an order of magnitude lower than the noise level of the existing system.(2)Based on the novel fully-differential neural recording front-end circuit and the high-density integrated wireless communication module,a miniaturized dual-channel high-performance wireless neural signal acquisition system is developed.The size of the microsystem is 9×7×5 mm~3 and the weight is 955 mg.Compared to the reported implantable brain-computer interface microsystems,the volume and weight are reduced by 86%and 66%,respectively.Biological experiments show that the wireless neural recording microsystem can be used to collect LFP and spike signals of rats in the free state.(3)A linear power regulation magnetically coupled resonant wireless power transfer system structure is proposed to improve the efficiency of wireless power transfer for implants.Based on the gyroscope theory,the link parameters of wireless power transfer are analyzed,and then the linear changes of the wireless power transfer link parameters are realized by adjusting the voltage regulation structure of the receiver.Simulation results show that the proposed linear power regulation system can decrease the frequency mismatch and the optimal load value deviation in wireless power transfer,improving the wireless power transfer efficiency and reducing the heating of the implant in the living body.(4)A miniaturized magnetic coupling resonance wireless power transfer system with linear power regulation is developed,which can realize linear power regulation of wireless power supply.The wireless power transfer system includes a miniaturized class-D power amplifier,and the transmission power of the wireless power transfer system is adjusted by adjusting the DC-DC output voltage.The test results show that the wireless power transfer system can realize the linear change of the receiver power when adjusting the transmission power,and the receiver efficiency is≥80%.The transmitting end of the wireless power supply system is 35 mm in diameter,which can be worn on the head of small animals such as rats to realize the free movement of organisms in a wider range.