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

Abstract

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 (Formula presented.) m to 5 (Formula presented.) 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.