CMOS Bioelectronics for Optical Neural Interfaces

Optical neural interfaces offer several advantages over electrophysiological methods for bidirectional interrogation of neural circuits such as cell-type specificity, reduced crosstalk and high spatiotemporal resolution with large fields of view. Integration of genetically encoded indicators and light-sensitive opsins allows for all-optical investigation of neural dynamics, advancing both fundamental neuroscience research and therapeutic applications. In this paper, we present two implantable optical brain interfacing systems capable of optical functional imaging and optogenetic stimulation based on single-photon avalanche diodes (SPADs) monolithically integrated with complementary metal-oxide semiconductor (CMOS) integrated circuits (ICs). The Subdural CMOS Optical Probe (SCOPe) is an implantable surface device that can span multiple brain regions in large animal models with >45 mm² field-of-view (FoV). We also present Acus, a needle-like, 4.1-mm-long CMOS-based penetrating device that allows imaging at depth in brain issue by implanting the imager, obtaining FoV advantages over graded-index (GRIN) lenses with significantly less tissue displacement. Both devices integrate photodetectors, light sources, and optical filters in ultrathin packaging for minimal invasiveness. SCOPe is <200 µm thick, fitting into the subdural space, and Acus is <100 µm thick, supporting deep brain interfacing with minimal tissue damage. These devices support up to 400 frames-per-second (fps) operation; SCOPe is designed for mesoscopic imaging, and Acus enables the detection of single-neuron activity by utilizing advanced fluorescent reporters with fast dynamics.