Silicon Probes and Thin-Film Grids
Covers Silicon Probes, Thin-Film Grid Electrode and Electrocorticography.
Silicon Probes
A silicon probe is a microfabricated neural interface: one or more thin silicon shanks with discrete electrode sites at lithographically defined positions. Each site forms an electrochemical interface with tissue at a known depth and lateral offset, recording extracellular potentials or passing stimulus current.
Silicon probes are made by thin-film microfabrication: conductive and insulating layers deposited on a silicon substrate and patterned by photolithography, which reproduces feature geometry wafer to wafer. The mask set fixes the probe geometry — shank width and length, site area, and the spatial layout of sites along the shank — so geometry is established at fabrication rather than at assembly and is invariant within a design.
Neural interfaces are not one size fits all; function follows fit. The design space is large, and precision and reproducibility let a geometry be designed against a specific neural target: sites along a shank for laminar profiling, clustered so that one unit appears on several sites, replicated across parallel shanks, or arrayed over a platform to sample a volume. The catalog holds 216 designs: 4 to 1,024 iridium sites, 1 to 16 shanks, 1.5 to 60 mm.
Probe quality is the product of the microfabrication process, the design details, and the package assembly. A design becomes an orderable probe only when paired with a package. Research use only.
Thin-Film Grid Electrode
A thin-film grid electrode is a flexible polymer electrode array designed for skull-surface EEG, epidural, or subdural ECoG recording and/or surface stimulation. Multiple electrode sites record biopotentials or deliver stimulation current.
Why it matters: Thin-film grids provide conformal contact with curved brain or skull surfaces, enabling high-density surface recordings that capture neural activity across large cortical areas with minimal tissue damage.
Key specifications: Site count, spacing, total area, substrate material (polyimide or parylene), and site material determine spatial resolution and signal quality. Available in custom layouts for specific brain regions.
Applications: Chronic EEG monitoring, intraoperative ECoG mapping, brain-machine interface research, and spinal cord surface recording.
Electrocorticography
Electrocorticography (ECoG) records electrical activity from the brain surface using grid or strip electrodes placed epidurally (on top of the dura) or subdurally (beneath the dura, directly on the cortex).
Why it matters: ECoG provides higher spatial resolution and signal quality than scalp EEG while being less invasive than penetrating probes. It is used in both clinical neurosurgery (epilepsy mapping) and research (brain-machine interfaces, sensorimotor mapping).
Signal characteristics: ECoG captures local field potentials with bandwidth up to several hundred Hz, including high-gamma activity (70–200 Hz) that is not accessible with scalp EEG.
NeuroNexus products: Thin-film grid electrodes provide flexible, high-density ECoG arrays for both acute and chronic surface recordings.