Optimization of the Geometry and Porosity of Microelectrode Arrays for Sensor Design

This paper describes the systematic investigation of a range of microelectrode arrays with varying dimensions fabricated by standard photolithographic and reactive-ion etching techniques. As expected from theory, the electrochemical behavior of microelectrode arrays with a constant individual diameter varied strongly with center-to-center spacing, the larger the spacing the more sigmoidal the recorded voltammogram. Furthermore, the behavior of arrays with a constant relative center-to-center spacing is shown to vary with individual electrode diameter, the arrays with the smallest electrodes producing strongly peaked voltammograms. Peak current densities and signal-to-noise ratios were also obtained for a variety of array geometries, and the use of electrodeposited platinum black electrodes was investigated. To demonstrate one advantage of using a loosely packed microelectrode array in electroanalysis, a ferrocene-mediated enzyme-linked assay involving the biocatalytic reduction of H2O2 was investigated. Results showed an improved temporal response, with current−time transients reaching a steady-state response more quickly using arrays with increased center−center spacings.