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

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.

A silicon neural probe fabricated using DRIE on bonded thin silicon.

A silicon neural probe fabricated using a deep reactive ion etching based process on 250 μm thin silicon wafers was developed. The fabricated probes replicate the design of soft parylene-C based probes embedded in dissolvable needles and can therefore also be used to test the encapsulation properties of parylene-C in-vivo without introducing additional effects introduced by the dissolvable gel. The process also demonstrates the possibility of performing conventional photolithography on substrates bonded to a handle wafer using a backgrinding liquid wax (BGL7080) as an adhesive.

Ultra-miniature ultra-compliant neural probes with dissolvable delivery needles: design, fabrication and characterization.

Stable chronic functionality of intracortical probes is of utmost importance toward realizing clinical application of brain-machine interfaces. Sustained immune response from the brain tissue to the neural probes is one of the major challenges that hinder stable chronic functionality. There is a growing body of evidence in the literature that highly compliant neural probes with sub-cellular dimensions may significantly reduce the foreign-body response, thereby enhancing long term stability of intracortical recordings.

Ultra-compliant neural probes are subject to fluid forces during dissolution of polymer delivery vehicles.

Ultra-compliant neural probes implanted into tissue using a molded, biodissolvable sodium carboxymethyl cellulose (Na-CMC)-saccharide composite needle delivery vehicle are subjected to fluid-structure interactions that can displace the recording site of the probe with respect to its designed implant location. We applied particle velocimetry to analyze the behavior of ultra-compliant structures under different implantation conditions for a range of CMC-based materials and identified a fluid management protocol that resulted in the successful targeted depth placement of the recording sites.