Schematic diagrams of ITO, transparent gold, and DLC amperometric electrode geometries. ITO and gold electrodes were fabricated in both the four-electrode (A) and single-electrode (B) geometries. Electrodes are indicated in red and the insulation (photoresist) in a blue pattern. (C, D) Color differential interference contrast (DIC) images of ITO four- and single- electrode devices fabricated on glass coverslips. The bright fringes around the edges of the ITO electrodes in (C) are caused by a change in thickness near the edges of the electrodes due to the fabrication process. (E, F) Color DIC images of ultrathin gold electrodes fabricated in both geometries (A, B) on glass coverslips. (G) Schematic of DLC electrode fabrication geometry. (H) DIC image of a DLC electrode.