Deconstructing impedimetric drift towards signal stability for a porous 3D flow-through microelectrochemical biosensor

Measuring consistent impedimetric signals under flow remains a persistent challenge in microfluidic electrochemical impedance spectroscopy (EIS) due to dynamic signal drift. This becomes even more challenging in the presence of redox probes or complicated electrode geometry. Such drift complicates data analysis and undermines the reliability of the impedance sensor. As its underlying origins are insufficiently understood, drift corrections are not implemented, leading to false positives and false negatives. In this work, we investigate the sources of this drift in the EIS signal of a porous, flow-through microfluidic sensor with three-dimensional electrodes. For empty channels under flow conditions, unexpected drift was observed only in the presence of a redox probe, highlighting the central role of redox-mediated interfacial processes. Surprisingly, even in the absence of a redox probe, packed channels still exhibited significant electrochemical drift. Comparing EIS signals from packed and empty channels with and without the redox couple, we can decouple the contributions of flow, porous packing, and faradaic reactions on the origins of the drift. We hypothesize that the drift arises from the combined effects of convection, interfacial double-layer formation within the porous packing, and redox probe–electrode interactions. A new root-mean-square error based analysis framework is introduced to quantify drift and determine stable measurement windows, independent of sensor geometry or equivalent circuits. This algorithm is validated using single-stranded DNA detection that clearly illustrates that drift correction in EIS data significantly improves measurement reliability, and ultimately sensor selectivity, leading to fewer false positives or false negatives.