A versatile microfluidic electrochemical platform for diffusion-controlled, quasi-one-dimensional interfacial studies

We present a quasi-one-dimensional microfluidic electrochemical platform that suppresses convection through microscale confinement and eliminates electric field singularities by combining thin film electrodes with a dielectric overhang that shields the top surface of the electrode. This is important as dynamic electrochemical processes emerge from the coupled interplay between ion transport and interfacial kinetics, yet most experimental configurations cannot simultaneously enforce diffusion-dominated conditions and directly visualize the evolving interface. Electrostatic simulations identify an optimal overhang length range that minimizes field intensity and angle variations while maintaining mechanical stability, yielding an approximately equipotential electrode with field lines nearly normal to the interface. To demonstrate the concept, we fabricate a representative device using sputtered Cu/W electrodes and a low stress, pinhole free dielectric stack of alumina and silicon nitride. Using copper electrodeposition as a model system, in situ optical imaging tracks morphological evolution and front motion, while difference image analysis enables quantitative verification of mass conservation between anodic dissolution and cathodic growth under diffusion-dominated conditions. Cells incorporating the dielectric overhang exhibit mass balances consistent with quasi-one-dimensional transport. This modular architecture, compatible with different metal-electrolyte-dielectric combinations and advanced imaging modalities, provides a versatile platform to systematically investigate transport and interfacial phenomena in electrochemical systems.