A novel technique for increasing charge injection capacity of neural electrodes for efficacious and safe neural stimulation

Neural prostheses require chronically implanted small area penetrating electrode arrays that can stimulate and record neural activity. The fundamental requirement of neural electrodes is to have low interface impedance and large charge injection capacity (CIC). To achieve this fundamental requirement, we developed a novel technique to modify the surface of the Utah Electrode Array (UEA) to increase the real surface area without changing the geometrical surface area. Pt was coated on modified and unmodified (control) UEAs and electrochemical characterization such as impedance and CIC was measured and compared. The surface modified electrode impedance and CIC was ~188 Ohm and ~24 mC/cm² respectively. Increasing the real surface area of electrodes decreases the impedance by 1000 times and increases the CIC by 80 times compared to the control samples. The CIC of modified UEA was significantly higher than of any material reported in the literature, higher than sputtered iridium oxide (4 mC/cm²) or PEDOT (15 mC/cm²).