Substrate-integrated microelectrodes with improved charge transfer capacity by 3-dimensional micro-fabrication

Arrays of microelectrodes with high charge transfer capacity have been fabricated and characterized. Nano-porous titanium nitride thin films were deposited onto a 3-dimensional micro-fabricated structure etched into a biocompatible polyimide insulation layer. The polymer layer was micro-patterned by electron beam lithography and etched in an oxygen-plasma. Measurements at 1 kHz/100 mV in electrolytic solution (PBS) show a significant reduction of impedance by a factor of 0.3 to 0.2 and are in good agreement with the surface gain expected from the 3-dimensional micro-pattern. The influence of the series resistance of the buffer solution on the electrode impedance is also examined by impedance spectroscopy and finite element simulation. This kind of microelectrodes may finally be used for stimulation and recording of cells and tissue.