UC San Diego

Advances in neural engineering are enabling targeted neural recording and stimulation towards high-resolution brain computer interfaces. High-throughput bidirectional communication to the brain is paramount to reach translational impact with neural prostheses. Useful vision restoration through microelectronic retinal prosthesis implants continues to be a difficult challenge despite commendable attempts. Achieving practical control of thousands and millions of electrode channels calls for architectural advances to improve the scalability of biopotential recording, power, wireless communications, and biocompatible interconnect. This dissertation presents an interdisciplinary approach towards high-resolution retinal prostheses that overcomes these challenges. The requirements and interactions between biopotential recording circuits and electrodes are formulated in the context of neural recording. Next, a resonant inductive power transfer link for retinal prostheses is designed and validated. The effect of ocular movements on the efficiency of power transfer is demonstrated in a constructed phantom frame. Subsequently, a novel integrated circuit is designed and fabricated to provide highly energy-efficient power delivery and waveform control to drive a nanowire-based microphotodiode subretinal electrode array. Energy efficiency and scalability of the power and communication link is accomplished through external control over global stimulation waveform parameters. Efficiency improvements derive from two main approaches: adiabatic unregulated power delivery to the stimulator, and duty cycling of the external transmitter. Global charge metering and calibration minimize the required data transmission and system operating frequency for bidirectional communication and charge-balanced stimulation. The dissertation concludes with in vivo validation of the nanowire microelectrode array transducer in rabbits using the principle of synchronous detection of cerebral cortex visual evoked biopotential signals. The various components of this dissertation present a full-stack development of a system to remediate blindness and advance the field of neural interfaces.