Evaporation-driven Supraparticle Synthesis by Self-Lubricating Colloidal Dispersion Microdrops.

The surface-templated evaporation-driven (S-TED) method that uses liquid-repellent surfaces has attracted considerable attention for its use in fabricating supraparticles of defined shape, size, and porosity. However, challenges in achieving mass production have impeded the widespread adoption of the S-TED method. To overcome this limit, we introduce an evaporation-driven "multiple supraparticle" synthesis by drying arrays of self-lubricating colloidal dispersion microdrops. To facilitate this synthetic method, a hydrophilic micropattern is prepared on a hydrophobic substrate as a template. During the removal of the substrate out of a dispersion, liquid drops are trapped and generate a microdrop array. To produce supraparticles, the contact lines of the trapped drops must be able to recede freely during evaporation. However, hydrophilic micropatterns induce strong contact line pinning for microdrops that hinders supraparticle formation. Herein, we solve this contradiction by employing an Ouzo-like colloidal dispersion, where we can control the wettability of the drop trapping domain. The self-lubrication effect provided by the Ouzo-like solution enables smooth movement of the drops' contact lines during evaporation, thereby resulting in the successful fabrication of supraparticle arrays even within the trapping domain. This strategy offers a promising and scalable approach for large-scale evaporation-driven supraparticle synthesis with a potential for extension to various primary colloidal particles, further broadening its applicability.