Completely Parylene-Coated Neuroprobe for Chronic Recording

This work fabricated an 8-channel neuroprobe which was completely protected by biocompatible parylene in a novel way. Laser cutting, instead of conventional etching, was utilized to define the sharp tip. After bounding aluminum wires on the platinum electrodes, the neuroprobes were fully insulated by parylene. Then, aluminum wires were broken by shear force and etched out chemically to expose the platinum electrodes. By the merit of conformal parylene coating, the neuroprobe tip is exactly protected and insulated from the ambient except the portion of the Pt electrodes. The fabricated neuroprobe is 7-mm long, 0.5 times 0.5 mm² of cross-section and with 8-channel electrodes of 50 mum size for each. The resistance and the capacitance of the microelectrode are 111.01 plusmn 55.89 kOmega and 0.1376 plusmn 0.064 muF, respectively. The small resistance and large capacitance is due to the relatively large of the metal wire, which is larger than that of Michigan probe (al times 16-3 mm 100-177, Neuronexus Technologies). The neuroprobe was inserted into the rat´s primary sensory cortex for acute recording of neuronal activities. Potentials evoked by mechanical stimulation which was applied on the receptive field were recorded. Based on the consideration that parylene has good biocompatibility and thus less tissue damage, we believed that this probe could serve the purpose of long-term recording.