Characterization of parylene-C film as an encapsulation material for neural interface devices

Neural interfaces, devices that interact with nervous system, have been studied to help patients with neural disorder to restore lost neural function. The neural interface device requires a conformal, biocompatible and chronic stable encapsulation layer to protect the device electronics and to isolate electrical signals from the interference of other electrodes as well as the physiological electrolyte. Parylene-C films deposited by a chemical vapor deposition system were studied as the encapsulation layer for neural interface devices. Impedance spectroscopy and leakage current test were used to investigate the encapsulation performance of Parylene-C films, and the results showed hermetic protection as well as long term stability of the films. The adhesion between Parylene-C and the silicon substrate was studied by tape adhesion test, which suggested that thermal stress impaired the adhesion force. The oxygen plasma etching process was studied to conformally remove Parylene-C encapsulation from the electrode tips, and the tip exposure versus electrode impedance was investigated. Parylene sample was kept in an accelerated environmental chamber condition, 85% RH and 85°C, for 500 hours, and the film did not show appearance change under.