Insulation of thin-film parylene-C/platinum probes in saline solution through encapsulation in multilayer ALD ceramic films.

Biomed Microdevices

Department of Electrical and Computer Engineering, Carnegie Mellon University, 5000 Forbes Avenue, Pittsburgh, PA, 15213, USA.

Published: July 2018

The long-term electrical leakage performance of parylene-C/platinum/parylene-C (Px/Pt/Px) interconnect in saline is evaluated using electrochemical impedance spectroscopy (EIS). Three kinds of additional ceramic encapsulation layers between the metal and Px are characterized: 50 nm-thick alumina (AlO), 50 nm-thick titania (TiO), and 80 nm-thick AlO-TiO nanolaminate (NL). The AlO and TiO encapsulation layers worsen the overall insulation properties. The NL encapsulation layer improves the insulation when combined with a TiO outer layer to promote adhesion to the Px. Experiments are performed with various insulation promotion treatments: A-174 silane (A174) treatment before Px deposition (to promote adhesion); SF plasma treatment (F) after Px deposition (to increase hydrophobicity); and ion-milling descum (IM) after Px deposition (to prevent parylene oxidation). A174 and F treatments do not have a significant impact, while IM leads to worse insulation performance. A circuit model elucidates the insulation characteristics of Px-ceramic-Pt-ceramic-Px interconnect. These studies provide a foundation for processing ultra-compliant neural probes with long-term chronic utility.

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Source
http://dx.doi.org/10.1007/s10544-018-0307-3DOI Listing

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