High-density electrical and optical probes for neural readout and light focusing in deep brain tissue

TLDR

The study aims to create high‑density neural probes that enable simultaneous single‑cell electrophysiology and optogenetic manipulation while minimizing tissue damage. Using a common substrate, the authors micro‑fabricated 47‑µm‑wide, 16‑µm‑thick shank probes with dense electrodes and integrated single‑mode waveguides, and proposed a method to combine both functions into one device. The resulting devices feature 64‑pad electrical probes with 120‑nm interconnects and 5×25‑µm pads, and optical probes with 250×160‑nm waveguide cores that focus light into 2.35‑µm spots via two on‑shank gratings.

Abstract

To advance neuroscience in vivo experiments, it is necessary to probe a high density of neurons in neural networks with single-cell resolution and be able to simultaneously use different techniques, such as electrophysiological recordings and optogenetic intervention, while minimizing brain tissue damage. We first fabricate electrical neural probes with a high density of electrodes and small tip profile (cross section of shank: 47-μm width × 16-μm thickness). Then, with similar substrate and fabrication techniques, we separately fabricate optical neural probes. We finally indicate a fabrication method that may allow integrating the two functionalities into the same device. High-density electrical probes have been fabricated with 64 pads. Interconnections to deliver the signal are 120-nm wide, and the pads are 5 × 25 μm. Separate optical probes with similar shank dimensions with silicon dioxide and silicon nitride ridge single-mode waveguides have also been fabricated. The waveguide core cross section is 250 nm × 160 nm. Light is focused above the waveguide plane in 2.35-μm diameter spots. The actual probes present two output focusing gratings on the shank.