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 and water-soluble surfactants. These vesicles of clay are mechanically robust and are stable in water and other liquids. We find that the wetting of organic liquids on clay explains the formation of clay vesicles from clay armored bubbles. Clay vesicles are microporous, exhibit size-selective permeability, and support 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.