We report a sensor platform based on a closed bipolar electrochemical circuit employing electrochemiluminescence detection and square-wave excitation that allows signal averaging to achieve high sensitivity. The cell is comprised of a bipolar electrode fabricated using photolithography that spans sensing and reporting compartments constructed using a 3D printer. The square-wave technique allows an electroactive analyte to be regenerated by applying a reverse potential, thus allowing significant S/N gains by accumulating ECL signals over multiple measure-regenerate cycles. The working principles of the SW-BPE sensor were demonstrated using Fe(CN)₆³⁻ as a representative analyte. Using DNA self-assembled monolayers as a model for the electrochemical proximity assay co-developed in our laboratories, we demonstrate the ability to detect ca. 300 fmol/cm² of MB-conjugated DNA. The square wave ECL sensor described herein is capable of detecting a wide variety of analytes over broad concentration ranges, and shows great promise for a variety of analytical applications.