Semi-permeable vesicles composed of natural clay

We report a simple route to form robust, inorganic, semi-permeable compartments composed of montmorillonite, a natural plate-like clay mineral that occurs widely in the environment. Mechanical forces due to shear in a narrow gap assemble clay nanoplates from an aqueous suspension onto air bubbles. Translucent vesicles suspended in a single-phase liquid are produced when the clay-covered air bubbles are exposed to a variety of water-miscible organic liquids. These vesicles of clay are mechanically robust and are stable in water and other liquids. The formation of clay vesicles can be described by a physical mechanism that recognizes changes in the wetting characteristics of clay-covered air bubbles in organic liquids. The clay vesicles are covered with small pores and so intrinsically exhibit size-selective permeability, which allows spontaneous compartmentalization of self-assembling molecules in aqueous environments. The results we report here expand our understanding of potential paths to micro-compartmentalization in natural settings and are of relevance to theories of colloidal aggregation, mineral cycles, and the origins of life.