Parylene Photonic Neural Probes

In this project, we are developing high-density flexible optoelectrical neural probes capable of electrophysiology recording and optical stimulation with high spatiotemporal resolution. These neural probes consists of an electrical layer with high density of passive recording electrodes and a photonic layer. The photonic layer has an array of compact polymer waveguides.
Our neural probes consist of 64 channel silicon shanks, monolithically integrated compliant flexible cables, and a stiff backend that can be integrated with the recording headstage circuitry. Our scalable fabrication process based on high resolution DUV lithography is optimized on different fronts to develop reliable neural probes.
The manufacturing process and the post-fabrication assembly are optimized so that a large number of these neural probes can be made available to a wide user base. We are testing these probes for full-volume sampling of a mouse visual cortex in V1 and HVAs. Optical functionality will be added by integrating on-chip photonic waveguides and optical switch banks. Using integrated photonic techniques, we can design novel architectures for implantable neural probes based on biocompatible materials to realize higher density probes that can be actuated while in the brain.
We have also recently developed fully flexible high density neural probes for chronic recording of neuronal activity in non-human primate NHP brain (more coming out soon):
These probes are realized on thin Parylene C substrates.
We characterize the electrochemical impedance spectrum of these probes using a custom-built EIS measurement setup:
We can further reduce the impedance by electrodeposition of conductive polymers.