Layer 7-T

The Layer 7-T is a temporary cortical electrode array (for use less than 30 days) placed on the surface of the brain to record, monitor, and stimulate electrical signals. It consists of a thin-film polyimide substrate with 1024 platinum electrodes connected to a rigid PCB headstage via ribbon cables, and connects to standard EEG equipment through a yoke cable and DIN connectors for brain mapping and epilepsy monitoring.

The Layer 7-T has 1024 electrodes with smaller contact diameters (0.05–0.5 mm) and tighter spacing (400 µm) compared to the predicate's 1–128 electrodes and 10 mm spacing. The substrate material is polyimide with platinum contacts (versus the predicate's silicone with platinum/iridium). It includes an integrated PCB bonded to the electrode array and a built-in pocket with surgical tools, whereas the predicate did not. Maximum stimulation charge density is ≤50 µC/cm² (versus ≤30 µC/cm² for the predicate).

ISO 10993-1 (biocompatibility), ISO 11135:2014 (ethylene oxide sterilization), IEC 60601-1:2005 and amendments (electrical safety), IEC 60601-1-2:2014+A1:2020 (EMC), ASTM F2096-11, F88/F88M-21, D4169-23, D4332-22, and F1980-21 (packaging and shelf-life), ANSI AAMI HE75:2009 (human factors).

Although the Layer 7-T has higher electrode density, smaller dimensions, and uses polyimide instead of silicone, biocompatibility testing, GLP animal implantation studies in swine (comparing 1- and 6-week durations), bench testing (electrochemical performance, signal-to-noise ratio), and platinum dissolution testing all demonstrate safety and performance equivalent to the predicate Ad-Tech subdural electrodes. The increased charge density remains within safe limits per Shannon criteria and bench performance verified equivalence. The technological differences do not raise new safety or effectiveness questions because the PCB is passive (outside the body and enclosed), the smaller electrode footprint is offset by controlled charge density limits, and animal pathology showed no increased neurotoxicity versus the predicate.