Spreading- and evaporation-mediated 2D colloidal assemblies on fluid interfaces

Abstract

Fluid interfaces exhibit remarkable capabilities and significant application prospects in fabricating two-dimensional (2D) materials and colloidal assemblies. However, the efficient realization of the fluid-mediated self-assembly of colloidal particles has become challenging owing to the complex evolution of spatiotemporal processes and dynamic behaviors at fluid interfaces. In this study, we hypothesized that the superspreading of a volatile droplet directed the ultrafast self-assembly of colloidal particles on an insoluble fluid interface. To validate this hypothesis, employing high-speed and large-field microscopic observation experiments in tandem with theoretical analysis, the time evolution processes of droplet spreading, evaporation, dewetting, and particle assembly were captured, and the multi-scale dynamic behavior of volatile colloidal droplets on an immiscible liquid substrate was studied. Our findings revealed the power law of droplet spreading dynamics at the macroscale, evaporation-induced dewetting of the liquid film and aggregation of colloidal particles at the mesoscopic scale, and colloidal self-assembly under the action of capillary and DLVO forces at the microscopic scale. Moreover, we realized the ultrafast fabrication of 2D colloidal assemblies on liquid interfaces. This work presents a simple, robust, and efficient method for self-assembling and manufacturing 2D-ordered structures and materials based on a platform of fluid interfaces.