Electroanalysis in a dissolving microdroplet.

Electroanalytical chemistry has increasingly focused on probing dynamic, non-equilibrium processes that remain difficult to access using conventional approaches like bulk measurements where the electrolyte and evaporation/dissolution processes are approached as static. Recent advances have extended these capabilities to the single-entity level through stochastic electrochemistry. Within this framework, microdroplet-based systems have emerged as powerful platforms for studying confined chemical processes at electrified interfaces, particularly in biphasic environments. Here, we introduce dissolving microdroplet electroanalysis as an emerging approach for interrogating multiphase interfacial dynamics. Unlike conventional assumptions of stability, individual microdroplets confined to electrified microinterfaces do not remain static but continuously dissolve, evolving in size, composition, and interfacial area during measurement. This dynamic tranformation directly generates electrochemical signals that encode interfacial transport and reaction processes occuring inside the confined volume, and at the liquid-liquid and liquid-solid phase boundaries. We found that this framework enables quantification of microdroplet lifetimes, extraction of liquid-liquid diffusion coefficients, and access to nanoscale fluctuations associated with dynamic slipping events at the multiphase boundaries. We also show that a dissolving microenvironment enables intrinsic concentration enrichment and biphasic catalytic amplification, achieving detection down to attomolar concentrations and, in some cases, approaching fewer than 1000 analyte molecules. By directly linking microdroplet evolution to electrochemical response, this approach establishes a versatile platform for probing interfacial reactivity, transport, and transient chemical states in evolving volumes and motivates broader adoption for uncovering physicochemical phenomena that remain inaccessible using conventional methods.