Redox Cycling at an Array of Interdigitated Bipolar Electrodes for Enhanced Sensitivity in Biosensing

An array of many bipolar electrodes (BPEs) can be controlled by a single pair of driving electrodes yet allows for multiplexed analysis of many individual biomarkers or single cells at once. A wide range of bipolar electrochemical sensors have been devised, many of which operate under battery power and produce visible signals (e. g., luminescent, electrochromic) appropriate for smartphone or naked eye readout. These features of BPEs are advantageous in the context of clinical and environmental sensing applications at the point of need. However, the sensitivity of BPEs is poor in comparison to direct measurement of current at an individual electrode, and therefore, the enhancement of signals obtained at BPEs is an active area of research. Here, we describe signal amplification by redox cycling accomplished by interdigitation of each BPE in an array with a shared driving electrode. We evaluate amplification obtained for interelectrode spacing in the range of 35 μ m to 5 μ m, over which the limit of detection decreased by an order of magnitude. Each interdigitated BPE (IDBPE) in the array has an independent, reproducible, and linear response to a reversible electroactive analyte. Therefore, this universal amplification strategy allows for multiplexed or spatially resolved sensing in point‐of‐need applications. Interdigitation of the sensing poles of an array of bipolar electrodes (BPEs) with a shared driving electrode allows for redox cycling, which amplifies the intensity of electrochemiluminescence (ECL) generated at the reporting poles. This approach retains the advantages of ECL at BPEs, which include simple optical readout amenable to the point of care and the capacity for multiplexed sensing, while introducing an exponential gain in signal with decreasing gap size. This added sensitivity is anticipated to broaden the range of bioassays for which ECL at BPEs is relevant.