Nanostructured / porous coating

A broad class of surface treatments, including nanoporous metals, sponges, dendritic or fractal deposits, sintered particles, and templated foams, engineered to maximize electrochemically active area within a fixed geometric footprint. Because interface impedance falls and charge capacity rises with real (not projected) area, roughening the surface at the nanoscale is the most general lever for improving a contact regardless of the base material.

The design tension is pore accessibility: nanoscale roughness helps low-frequency and steady-state charge storage, but if pores are too fine or tortuous, ionic access is diffusion-limited and the extra area does not help at the kHz frequencies of spikes or the fast edges of stimulation pulses. Good coatings therefore tune pore size and hierarchy to the relevant timescale, rather than merely maximizing surface area.