Hierarchical Surface Restructuring of Ultra-Thin Electrodes and Microelectrode Arrays for Neural Interfacing with Peripheral and Central Nervous Systems

Long-term implantable neural interfacing devices are crucial in neurostimulation for treating various neurological disorders. These devices rely heavily on electrodes and microelectrode arrays. As the invasiveness of these electrodes increases—particularly for peripheral and central nervous system applications—both potential benefits and risks of adverse side effects to the patient rise. To mitigate risks and enhance device performance and longevity, electrodes for such invasive applications must be thin, flexible, and have small contacts. However, these features typically reduce the geometric surface area and electrochemical performance of the electrodes, diminishing treatment benefits. This report explores the feasibility and advantages of using femtosecond laser hierarchical surface restructuring (HSR) technology to improve electrochemical performance without compromising the structural integrity of ultra-thin (<25 µm) platinum-iridium alloy (Pt10Ir) electrode contacts. In this report, an HSR process is developed that significantly enhances the electrochemical performance of 20 µm thick Pt10Ir electrodes by controlling the depth of restructuring. A comprehensive characterization is conducted to assess the surface, sub-surface, morphological, microstructural, and electrochemical properties of these restructured electrodes using multiple characterization modalities. This evaluation aimed to assess the electrodes' performance and to identify features that promote efficient electron transfer, high electrochemical surface area, excellent electrochemical performance, and biocompatibility.