Using liquid-in-liquid 3D printing for fabrication of bijels induced by solvent transfer induced phase separation

Bicontinuous interfacially jammed emulsion gels (bijels) are a new class of soft material first introduced in 2005. These materials have beneficial properties primarily because of the larger contact area along the interface of the two interwoven phases and within a small volume. Despite such promising properties, the fabrication of bijels has proved to be time-consuming and challenging due to the limits in selecting constituent materials, which confines their wide applications. Furthermore, bijels reported in the current literature are created in bulk and lack complexity in designs and shapes, which is another limiting reason. In this study, the fabrication of bijels is presented using solvent transfer induced phase separation methods (referred to as STRIPS) with various oil components (such as fatty acids and phthalates), nanoparticles (with different sizes and charges), and surfactants (cationic and anionic). Using the liquid-in-liquid 3D printing (LL3DP) technique, various structures with different designs and structural features were printed, and confocal/light microscopy images confirmed the formation of bicontinuous microstructures. Shear rheometry on the printed bijels characterized their mechanical properties and rheological behavior, suggesting robust shear-thinning gels. With the advancement presented in this work, bijels can find their way into various fields and for different applications, including energy, tissue engineering, catalysis, and separation.