Silicon Probe

It has 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 electrical microstimulation.

Silicon probes are made by thin-film microfabrication: conductive and insulating layers deposited on a silicon substrate and patterned by photolithography, which reproduces fine-feature geometry with sub-micron precision 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 probe geometry is established at fabrication rather than at assembly and is precise and invariant within a design.

The silicon probe descends from the Michigan probe developed at the University of Michigan (Wise et al. (1970); Drake et al. (1988)); NeuroNexus spun out of that program in 2004 and reported the first chronic performance of silicon probes in cortex (Kipke et al. (2003); Vetter et al. (2004)).

Micro-scale neural interfaces are not one size fits all; function follows fit. NeuroNexus has a large electrode design space, and precision and reproducibility let a geometry be designed against a specific neural target or application. The electrode catalog holds 216 designs: 4 to 1,024 sites, 1 to 16 shanks, 1.5 to 60 mm, on a 15 or 50 µm substrate.

Probe quality is the product of the microfabrication process, the design details, and the package assembly. Silicon probes are designed to penetrate the brain, spinal cord, nerves, ganglia or heart; their surface counterparts are thin-film grids. Research use only.

The material choices behind the platform, and the published evidence for each, are answered question by question in Silicon Probe Technology: Questions and Answers.