3D Printing of Bicontinuous Nanoparticle-Stabilized Emulsion Gels via Co-Solvent Removal

Bicontinuous emulsion gels are mixtures with interpenetrating arrangements of two immiscible liquids stabilized with particles. The structures of such gels are readily made into simple macroscale geometries, like sheets and fibers; however, achieving more complex macroscopic structures while maintaining control over microscopic features and morphological bicontinuity remains a challenge. In this study, the ability to fabricate complex 3D structures of bicontinuous emulsion gels using direct ink writing (DIW) is demonstrated. The emulsion precursors are formulated with a mixture of hydrophilic and hydrophobic fumed silica particles; these precursors exhibit shear-thinning and yield stress behavior necessary for DIW. The thixotropic nature of the precursor further promotes the formation of bicontinuous emulsion gels through vaporization-induced phase separation and stabilization through both interfacial jamming and bulk stabilization mechanisms. This fabrication technique enables the creation of functional bicontinuous structures with complex architectures, paving the way for application in biomedical implants, catalytic reactors, and beyond.