Unraveling stability of a floating liquid marble and its collapse patterns

Liquid marbles (LMs) are droplets of liquid usually enwrapped by hydrophobic particles. Our aim was to analyze collapse dynamics of floating LMs, stability and resulting collapse patterns. PTFE LMs were prepared by rolling a drop at a fixed angle and dynamics of the floating LM collapse was recorded. These LMs showed distinct collapse patterns and times by varying both the core liquid and the liquid substrate. Densely packed petal shaped patterns were obtained in the case of no surface tension gradient between those of core liquid of LM and supporting liquid substrate. On the other hand, porous and diffuse patterns were obtained in the case of surface tension gradient. Aqueous solutions of methylene blue visualized the opening of dipped LM and led us to preparation of robust LMs which remained stable upto 6 hours after which they underwent buckling. Regime of collapse was divided into- petal, porous and buckled LM. Effective surface tension(γ_eff) was directly related to the stability of floating LM and estimating capillary forces(γ_int) gave us clues about the nature of interaction between both particle-particle and particle-liquid. Further, changing the temperature of the liquid substrate changed stability of LM without using any temperature responsive coating material.