Mechanically robust wrinkled liquid marbles

Abstract

Liquid marble (LM) is a droplet covered with jammed low-wettability fine particles, which exhibits non-sticking to contacting media while keeping its fluid reconfigurability. While the LM facilitated the handling of the droplet, LM breaks down upon squeezing, which limits the robust handling. Here, we show that LM exhibits high compression stability when the jammed particles distort the liquid surface to form sub- to single-micron roughness. We find that the particle layers' distortion increases with the evaporation of the inner liquid. Thus, we regulated the evaporation degree of the droplet by varying the mixing ratio of the nonvolatile and volatile liquids. First, we show the regulation of the mixing ratio and its effect on the equilibrium LM static shape and particle layer structure. Then, the effect of the LMs' surface structure on their mechanical response is explored. When 90% of the inner liquid is evaporated, the submicrometer wrinkle structure appears on the LM surface. We name the LM with the wrinkle structure “wrinkled liquid marble (WLM).” The WLM exhibited high compression stability and significantly higher resilience force than the droplet one. We believe this work helps the practical use of the LMs by improving their mechanical stability. Moreover, the fundamental understanding of the particle layer stability at the interface can be advanced.