Thermo-induced reversible nanoemulsification

Abstract

Nanoemulsions are prevalent in diverse fields, such as cosmetics, food, pharmaceuticals, oil recovery, drug delivery, and templated materials synthesis, due to their high kinetic stability and versatility in structures and compositions. However, nanoemulsions remain thermodynamically unstable and gradually undergo irreversible breakdown, posing significant constraints on their applicability. Inspired by the dynamic equilibrium of atmospheric clouds, we present thermo-induced reversible nanoemulsification of biphasic liquid systems through cyclic heating and cooling processes. With our strategy, nanodroplets dissipate through dissolution upon heating and re-emerge through nucleation upon cooling, driven by temperature-dependent solubility. Combining experimental, numerical, and theoretical studies, we identify the critical conditions for nanoemulsification, elucidate the physicochemical mechanism of nucleation, and predict the size of nanodroplets. Thermo-induced nanoemulsification (TINE) offers a reversible, facile, and scalable method for energy-efficient, surfactant-free production of nanoemulsions, characterized by good emulsion stability, diverse emulsion types, and precise control over droplet size.