Mechanically Stable Fractal Microelectrode with Nanostructured Pt/PEDOT:PSS for a Reliable Neural Stimulation

Neural stimulation provides significant therapeutic benefits for patients with neurological disorders. PEDOT:PSS has gained attention as a neural electrode material, but its poor mechanical stability due to continuous cyclic charge injection, which is especially severe on ultrathin substrates, remains a big challenge for its clinical utility. To address this problem, we developed a mechanically and electrochemically stable PEDOT:PSS-based microelectrode for neural stimulation by utilizing enhanced adhesion on the vertical interface between the three-dimensional (3D) nanostructured substrate. Our microelectrode design incorporates a fractal geometry that increases the perimeter-to-area ratio, coupled with nanostructured platinum to enhance the surface area. The simple PEDOT:PSS-coated microelectrode exhibited outstanding mechanical stability, evidenced by various metrologies, such as scanning electron microscopy (SEM), energy-dispersive X-ray (EDX), and atomic force microscopy (AFM), which can facilitate wide industrial adoption. We further verified using numerical analysis that the fractal electrode with a nanostructured Pt/PEDOT:PSS coating outperforms the traditional PEDOT:PSS-coated circular electrode. This innovative combination of geometrical design and surface treatment introduces a novel approach to developing robust microelectrodes for reliable neural stimulation.