A MEMS-based flexible electrode array using composite substrate

We present a MEMS-based flexible subdural electrode array for neural recordings. The electrode array is fabricated on a composite substrate of polyimide and biomedical-grade polydimethylsiloxane(PDMS). The electrodes are deposited on polyimide layer, and the whole device is packaged by PDMS. Ablating with a CO₂ laser is applied to expose the electrodes sites. The surface of the electrodes is modified to increase the surface area, which can decrease interface impedance by nearly 90%. Prototypes of 2×4 and 2×1 arrays are fabricated with exposed electrode diameters of 0.5mm and 2.3mm respectively. After full package, the whole thickness of the electrode array is 0.7mm. For the 2×4 array, the average electrode impedance is 18.9 kΩ for normal 0.5mm electrodes and only 1.58kΩ for surface modified 0.5mm electrodes. The 2×1 array was successfully subdural implanted into a rabbit´s brain, and get its electro-corticogram(ECoG).