Associative Liquid-in-Liquid 3D Printing Induced by Surfactants Self-Assembly

Structuring oil-water interfaces to create hierarchical functional structures between fluidic interfaces has been a significant area of study in various material sciences and engineering fields. In the current research, we will introduce a new liquid-in-liquid 3D printing approach that utilizes self-assembly at the interface of surfactants in the aqueous phase and cosurfactants in the oil phase to create interfacial assemblies that are highly ordered, which makes the work distinguishable from other traditional 3D printing techniques or liquid-in-liquid printing methods. In this technique, extruding an aqueous solution of various surfactants into a stabilizing lipid bath can generate gel-like constructs with internal nanostructures. When the prepolymers are added into one of the phases followed by photopolymerization, the ordered nanostructures induced by surfactant self-assembly are persevered, confirmed by small-angle X-ray scattering (SAXS). Tunable mechanical properties are observed by changing constituent concentrations and types. We present the phase behavior and structure-properties relationship using shear rheometry, tensile measurements, microscopy, and SAXS. We will further explain the underlying stabilization phenomena and morphological phase transitions using experiments and dissipative particle dynamics (DPD) simulation.