Mechanism of multilayer formation on liquid marbles

Liquid drops encapsulated by particulate matter, which are referred to as liquid marbles, have been utilized as transportation vehicles for small amounts of liquids, miniaturized chemical/biological reactors and sensors. Liquid marbles are frequently stabilized by a multilayer of intrinsically liquid-philic particles that are highly agglomerated before contact with liquids. However, the conditions for the multilayer formation have not been elucidated. In this study, we prepared a model for agglomerated particles by assembling spherical glass particles with reasonably well-defined structures and controlled surface chemistries. We clarified that a multilayer was formed by the agglomerated particles, which shows a metastable Cassie-Baxter state. The robustness of metastable Cassie-Baxter states increased with decreasing particle intrinsic wettability properties against liquids. This led to the successful stabilization of liquid marbles with a multilayer. Finally, our results offered a criterion for the control of surface structures that alter the physical properties of liquid marbles.