Diffusion limited current in very high aspect ratio Pt needle electrodes

A direct-write nanofabrication technique was applied to fabricate high aspect ratio Pt needle electrodes for site specific electrochemistry and electrophysiology. Non-passivated and passivated (with a 10 nm thin insulating film) Pt needles having uniform radii as small as 100 nm and lengths over 30 m were deposited on the exposed conductive ends of ultramicroelectrodes to form extended needle electrodes. Diffusion limited current and its dependence on the radius of the Pt needle were measured with linear sweep voltammetry. Model fittings validated the function of such needle electrodes for effective microscale electrochemical studies and potentially electrophysiological applications.