Design, fabrication, and test of flexible thin-film microelectrode arrays for neural interfaces

This paper describes the design, fabrication, characterization and application of PET/ITO and polyimidebased flexible microelectrode arrays for recording purposes and also stimulation of retinal bipolar and ganglion cells. Two different structures are designed in this work. The planar electrode arrays are fabricated on thin PET/ITO and polyimide substrates and encapsulated with SU-8 which is a biocompatible passivating material. Stimulation and recording sites are made by platinum in order to reduce the electrode/tissue interface impedance. The utilized substrates make the fabricated electrodes so flexible that they can easily shape to contoured surface of retina. Prototypes of 6×6 electrode arrays are fabricated for recording from and stimulation of target tissue. The exposed electrode surface has a diameter of 100μm with tracking path width of 40μm and 15μm spacing between interconnects. Fabricated microelectrodes were characterized by impedance spectroscopy and also were used to record ECoG signals from anesthetized rat. Experimental results show the electrode/tissue impedance of 6.4kΩ at the frequency of 1kHz.