Perforated silicon membranes as an artificial neural contact pad-chip design and tissue implant response

Silicon membranes (diameter=4 mm, thickness=60 μm) with a circular matrix of holes centered at the chip were fabricated using anisotropic etching. The perforated area had a diameter of 2 mm. Three membrane geometries (hole sizes of 10, 50 or 100 μm) were investigated to find a suitable hole size for the nerve regeneration. The silicon membranes were mounted between two silicone rubber tubes and were implanted in the rat sciatic nerve for 4 or 16 weeks. The function of the regenerated nerve was investigated by measuring the muscle contractility force of the gastrocnemius muscle. The membranes with 100 μm holes displayed superior muscle force measurements compared to the chips with 10 μm and 50 μm holes. The 100 μm chip showed a 56% regained muscle force relative the uninjured contralateral side. Cross-sections of the regenerated structures were inspected by light microscopy and SEM. The biocompatibility of the silicon membranes was evaluated by analyzing the tissue reactions 10 days after insertion of the membrane in the rectus muscle of the rat. Titanium discs were used as a reference material. The study showed no obvious difference between titanium and silicon implants