Application of integrated SECM ultra-micro-electrode and AFM force probe to biosensor surfaces

The integration of scanning electrochemical ultra-micro-electrode (UME) with atomic force microscope cantilever probe have been achieved by using a homemade photolithography system. A gold-film-coated AFM cantilever was insulated with photo resist coating and a pointed end of the AFM probe was opened by illuminating with maskless arbitrary optical micro-pattern generator. To realize precise control of probe sample distance constantly, the resulting scanning electrochemical microscopy (SECM)–AFM probe was operated using a dynamic force microscopy (DFM) technique with magnetic field excitation. From a steady-state voltammetric experiment, the effective electrode diameters of the probes thus prepared were estimated to be from 0.050 to 6.2 μm. The capability of this SECM–AFM probe have been tested using gold comb in the presence of Fe(CN)63−. The simultaneous imaging of the topography and electrochemical activity of the strip electrode was successfully obtained. We also used the SECM–AFM to examine in situ topography and enzymatic activity measurement. Comparison of topography and oxidation current profiles above enzyme-modified electrode showed active parts distribution of biosensor surface.