These types of materials can be generated by application of an electrical field 15, using molding 4, 16, or direct ink writing (DIW) printing techniques 1, 6. Liquid-in-liquid printed materials 1, 2, 3, 4, 5, 6 have many potential applications in energy storage 7, 8, microreactors 9, and for creating biomimetic materials 10, 11, 12, 13, 14. Stabilized filaments are utilized for printing liquid-based fluidic channels. A scaling analysis based on the interplay between hydrodynamics and emulsification kinetics reveals that filaments are formed when emulsions are generated and remain at the interface during the printing period. The tube-like printed features have a spongy texture resembling miniaturized versions of “tube sponges” found in the oceans. We experimentally demonstrate the printed aqueous phase is emulsified in-situ consequently, a 3D structure is achieved with flexible walls consisting of layered emulsions.
Silica nanoparticles stabilize liquid filaments at Weber numbers two orders of magnitude smaller than previously reported in liquid-liquid systems by rapidly producing a concentrated emulsion zone at the oil-water interface. Here, we report a simple approach for creating stable liquid filaments of silica nanoparticle dispersions and use them as inks to print all-in-liquid materials that consist of a network of droplets. Current approaches are limited to drop-by-drop printing or face limitations in reproducing the sophisticated internal features of a structured material and its interactions with the surrounding media. Printing a structured network of functionalized droplets in a liquid medium enables engineering collectives of living cells for functional purposes and promises enormous applications in processes ranging from energy storage to tissue engineering.