A Reliable Wirelessly Powered CMOS Platform for Neural Recording

Safe, secure, and reliable neuronal measurements are highly desired for research and treatment of the human brain and central nervous system. Mice are often used as model organisms for research. This research leads to further investigation in humans or can be leveraged for applications, such as neurological diagnosis. Therefore, we seek a platform for measuring neural signals from mice. The platform should communicate wirelessly and should not require a local power source, e.g., a battery, for operation. The design should also emphasize safety and security. Finally, the system ideally will be small and highly integrated. Existing solutions suffer from limited power efficiency and thermal safety concerns.This work presents three improved rectifiers for future integration with the system. On 45 nm SOI, the initial Greinacher design was chosen for simplicity and demodulation compatibility. AC-coupling was then added to the output to improve low-power turn-on. Finally, on 180 nm Bulk CMOS, a modified cross-coupled design was pursued to achieve higher efficiency and output voltage, despite increased complexity. The performance and behavior of these designs in response to input frequency and load changes are discussed further. Additionally, this work explores using BEOL metal sensors in 180 nm CMOS to increase reliability in future systems. While the rectifiers transfer wireless power, the sensors ensure the resulting power dissipation does not compromise thermal safety, a critical requirement for chronic implantation. The sensors, implemented as a metal resistor network, overlay a mixed-signal circuit serving a critical system function. These networks enable temperature sensing and heat mapping, supporting development of more reliable wireless sensor systems.Efforts were made to improve the post-CMOS fabrication and integration of a custom-designed integrated circuit to produce this prototype. Integration and assembly methods are targeted toward biocompatibility and process yield improvements. System measurements, having a reconnectable flexible antenna and 45 nm SOI on-chip microelectrode array, are reported. Measurements were conducted before post-CMOS integration via on-chip probing, wirelessly in a controlled anechoic environment, and in a live mouse subject. This assembly shows promise for future use together with the previously mentioned RF frontend and thermal sensor network techniques on 180 nm Bulk CMOS.