Preparation of Morphology-Controlled Gel Particles from Small Molecules through Vortex Ring Freezing and Photopolymerization

A series of fluid intermediates with nonspherical shapes are produced when a droplet impacts the surface of a miscible liquid, and the fixation of these fluid intermediates through a gelation or precipitation process is known as the “freezing method”. However, the traditional existing vorticity ring derived gel particles were prepared from macromolecules and rely on chemical cross-linking reactions, limiting the choice of material. In this work, a strategy of preparing specially shaped gel particles by using a light-curable monomer through the methods of photopolymerization and vortex ring freezing was proposed. Based on the principle of matching the rapid reaction rate of light curing with the droplet deformation rate, a series of specially shaped (spherical, ellipsoidal, bowl, and tadpole) gel particles were prepared. The factors influencing droplet shape formation, such as light intensity, needle size, drop height, and the properties of the receiving bath, were analyzed. Three physical parameters, Reynolds number, Weber number, and viscosity ratio, were introduced to elucidate and predict the variations in gel particle morphology. This study opens up a green way for preparing specially shaped gel particles and holds promise for a wide range of future applications.