Theory of Microwell Arrays Performing as Generators–Collectors Based on a Single Bipolar Plane Electrode

Electroanalytical arrays of microwells with increased sensitivity and virtual immunity to interferents have been previously reported by us. Such arrays were designed to be operated in a classical generator–collector mode but exhibited also similar properties when their common planar collector was left floating. This evidenced that the unbiased collector acted as a bipolar electrode. In this work, a theory is elaborated to investigate in great detail the generality of this phenomenon and its limits. This establishes that if the analyte pertains to a redox couple with relatively fast electron rate constants, the bipolar collector results to be almost as efficient as when biased, thus suppressing the need for a bi‐potentiostat with obvious gain for analytical applications. Conversely, if the analyte rate constant of electron transfer is small, efficient operation in a bipolar mode remains feasible but requires a drastic decrease of the microwell density in the array.