A subnanolitre tetherless optoelectronic microsystem for chronic neural recording in awake mice

The long-term recording of neural activity could be used to understand complex behaviours and disorders. However, the development of technology capable of such measurements faces a variety of technical challenges, including the relative motion between recording electrodes and tissue and the excessive displaced volume from implanted electronics. Here we report a subnanolitre-volume tetherless optoelectronic microsystem for neural recording. The system relies on light for photovoltaic power and data transfer, through a light-emitting diode, eliminating the need for wires or other tethers. It uses a single AlGaAs diode as both photovoltaic and light-emitting diode. Complementary metal-oxide-semiconductor circuits provide low-noise amplification, pulse-position-modulated encoding and electro-optical transduction. Two-dimensional materials processing techniques, vacuum annealing and atomic layer deposition, in conjunction with a standard complementary metal-oxide-semiconductor fabrication process, provide compact encapsulation against the corrosive conditions of biological media. We show that the subnanolitre neural implant is capable of chronic (365 days) in vivo recordings in awake mice.