Figure 4.

Silicone electrode array molding procedure to combine multiple LCP-TF arrays together and provide soft edges to prevent damage to the cortex. (A) Illustrations of the electrode molding process. 1. Silicone primer was applied on the back side of the electrode and dried at room temperature for 30 min. 2. Double-sided polyimide tape was used to hold the alignment guide to the molding base. Double-sided transparent water soluble tape (PVA) was attached to the mold and the LCP-TF array to prevent silicone from covering the electrode contacts. A stencil was used to determine the shape and thickness of the silicone mold. 3. The LCP-TF array(s) were aligned and laminated onto the PVA tape using the alignment guide. 4. Well-mixed and degassed silicone was poured onto the mold. A wiper used to remove excessive silicone. 5. The silicone was cured at 60 °C for 2 h. 6. The assembly was soaked and rinsed with warm (>40 °C) DI water to remove the PVA tape and release the molded array. (B) SEM image of the cross section of a molded array showing the flat surface at the transition from the LCP-TF to silicone. Dust on the surface and side of the array were generated from the cross-sectional cut and not present normally. (C) Profilometer measurements of the electrode contact step height (Site) and the surface of the LCP-TF to silicone transition (Edge) showed a much flatter surface profile than conventional subdural clinical electrodes. (D) The LCP-TF prototype device was ∼11× less stiff than the commercial ECoG array. Maximum possible bending force that could be exerted on the brain derived from four-point bending tests and an analysis of brain geometry. A commercially available electrode array as well as an LCP-TF device prototype without Au traces were measured. The error bars indicate a standard error of means for all bending angles tested. The mean and SEM force for the LCP-TF prototype device was 6 ± 1 mN, while the commercial ECoG array force was 67 ± 17 mN.