BCIwiki (bciwiki.com) — According to the University of Central Florida, a study proposes selective protective coatings for three-dimensional pillar electrodes in the PRIMA retinal prosthesis. The preprint was posted on bioRxiv on September 10, 2026, and has not been peer reviewed. It focuses on treating gold pillar sidewalls while preserving the functionality of surrounding implant regions.
Pillar electrodes bring stimulating surfaces closer to inner retinal neurons, but exposed gold sidewalls present a biocompatibility problem. The authors explain that sputtering or atomic layer deposition cannot suitably protect the pillars selectively without also coating photosensitive regions and return electrodes. Their strategy uses non-critical photoresist lithography to protect planar return electrodes, followed by electrodeposition of titanium dioxide (TiO2) or platinum (Pt) onto the gold sidewalls.
The authors report that both TiO2 and Pt coatings were biocompatible in in-vivo studies and prevented adverse retinal tissue reactions to gold. They report a specific capacitance of 25 F/cm2 for electrodeposited TiO2, compared with 240 F/cm2 for Pt. The authors attribute better limitation of sidewall current to TiO2's lower capacitance, allowing charge injection to occur predominantly through the SIROF-coated pillar tops.
The authors describe the combination of electrodeposition and non-critical photolithography as a scalable wafer-level fabrication approach for biocompatible three-dimensional electro-neural interfaces. The tissue-response and electrical findings do not establish human clinical validation of the new coatings or demonstrate that they improve patients' vision.