Self-curling and -sticking flexible substrate for ECoG electrode array

We report a flexible electrocorticogram (ECoG) electrode array device with one directionally self-curling and -sticking properties, to solve the difficulty of the handling of thin (<; 10 μm) substrate devices (Fig. 1). As the substrate, we use sandwiched parylene-N/-C which films have different linear expansion coefficients. The thermal dependences of the deflection and curvature radius of the paylene-N/-C system were calculated. Based on the calculations, 2.5-μm parylene-N/2.5-μm paryelen-C “bi-parylene” flexible substrate was prepared. The self-curled substrate with the curvature radius of about 2 mm has been observed. The self-sticking of the curled device has been demonstrated on wet samples, due to the surface tension between the parylene-N and the sample. These results suggest that the bi-parylene substrate becomes a candidate material for easy-to-use flexible thin ECoG devices, enchaining the wrapping property over the brain.