Thin-Film Electrodes: Silicon Probes and Grids
NeuroNexus makes two kinds of microfabricated electrode arrays: silicon probes, which penetrate the brain, spinal cord, nerves, ganglia, or heart, and thin-film grids, which are positioned on the surface of the cortex, the skull, the heart, or a peripheral nerve.
Both types of electrodes are used for neural recording and/or stimulation. Some electrodes are effectively record-only or stimulation-only by design (e.g. modal limits on site sizes, spacing, or geometry). Other electrodes are capable of both recording and stimulation. They use similar thin-film microfabrication processes involving thin, micron to sub-micron thick, conductive and insulating layers deposited and patterned on a wafer. Both types of electrodes are available in many types of packages, such that they can be used in diverse applications and preparations.
Not all thin-film electrodes are equal. Electrode quality, and therefore performance, results from the microfabrication process, design details, package design and assembly, and quality manufacturing processes.
For electrode selection, the first consideration is the requirement for penetrating or surface neural interfacing, which generally depends on the tissue target, the signals of interest, and the preparation.
Silicon probes
A silicon probe has one or more thin silicon shanks with electrode sites at lithographically defined positions, so it records and/or stimulates at known positions along its shanks. Probe geometry and site layout are designed for the tissue target — laminar, clustered, multi-shank, 1D, 2D, or 3D, etc. NeuroNexus offers 216 catalog designs, 4 to 1,024 sites, 1 to 16 shanks, 1.5 to 60 mm, on a 15 or 50 µm substrate.
Thin-film polymer grids
A thin-film polymer grid is a flexible 12 µm-thick polyimide array that conforms to a surface and records the field potential on each site: NeuroNexus offers 53 catalog designs in four families — ECoG, EEG, cardiac, and nerve cuff.
Refer to How an Electrode Records Neural Activity for a primer on neural recording and to Silicon Probes and Thin-Film Grids: An Introduction for a technology overview. For research use only.
Typical values
| Silicon probes, catalog | 216 designs · 4–1,024 sites · 1–16 shanks · 1.5–60 mm · 15 or 50 µm |
|---|---|
| Thin-film grids, catalog | 53 designs · 4 families · 3–256 sites · 25 µm–1 mm sites · 12 µm polyimide |