PROPERTIES OF INTERDIGITAL ELECTRODE ARRAYS WITH DIFFERENT GEOMETRIES

Interdigital array (IDA) microelectrodes have been fabricated by photolithographic and electron-beam lithographic techniques on silicon substrates. Thin-film noble metal electrodes have been deposited on a titanium-adhesion layer. The electrode width and space varied between 1 and 2 mu m and between 300 nm and 1 mu m, respectively. These IDA electrodes were applied to voltammetric and chronoamperometric measurements of reversible redox species using a home-build free programmable multipotentiostat. The multiple oxidation and reduction of these compounds result in an increased current generation, where the collection efficiencies and the signal amplification of reversible redox molecules have been determined. Both parameters are dependent on average diffusion length. The measurement conditions, such as ionic strength and buffer composition, influence the amplification rate. Time resolved redox recycling experiments showed that the diffusion equilibrium strongly depends on the distance between generator and collector electrode. A high redox recycling rate and collection efficiency of the IDA spacing in the nm-range enable electrochemical measurements to be performed more sensitive and faster than conventional measurements. These measuring principle is attractive to enhance the sensitivity of biosensor based microsystems.