In situ study of water conductivity under evaporation-induced confinement using an interdigitated array electrode...

Understanding the fundamentals of water under nanoconfinement and finding a way to manipulate the properties of interfacial water are crucial to many processes and have attracted intense interest. Here, we demonstrate that the self-induced nanoconfinement arising during the final stage of evaporation of an aqueous droplet can be monitored in situ by using a millimeter-scale interdigitated array electrode sensor. Just before the complete evaporation, the confined water exhibits a conductivity enhancement of up to approximately an order of magnitude compared to bulk water. Moreover, this simple electrical readout provides a rapid and practical platform for screening aqueous electrolytes and colloids, enabling systematic investigation and manipulation of nanoconfinement-induced effects in water.