The ORCID identification number(s) for the author(s) of this article can be found under https://doi.org/10.1002/adma.202109547. Fluid-bicontinuous gels are unique materials that allow two distinct fluids to interact through a percolating, rigid scaffold. Current restrictions for their use are the large fluid-channel sizes (>5 µm), limiting the fluid-fluid interaction surface-area, and the inability to flow liquids through the channels. In this work a scalable synthesis route of nanoparticle stabilized fluid-bicontinuous gels with channels sizes below 500 nm and specific surface areas of 2 m 2 cm −3 is introduced. Moreover, it is demonstrated that liquids can be pumped through the fluid-bicontinuous gels via electroosmosis. The fast liquid flow in the fluid-bicontinuous gel facilitates their use for molecular separations in continuous-flow liquid-liquid extraction. Together with the high surface areas, liquid flow through fluid-bicontinuous gels enhances their potential as highly permeable porous materials with possible uses as microreaction media, fuel-cell components, and separation membranes.

Functionalized silica nanoparticles with or without in situ surface modification are used to fabricate bijels via solvent transfer induced phase separation (STrIPS).

Bicontinuous particle-stabilized emulsions (bijels) are networks of interpenetrating oil/water channels with applications in catalysis, tissue engineering, and energy storage. Bijels can be generated by arresting solvent transfer induced phase separation (STrIPS) via interfacial jamming of nanoparticles. However, until now, STrIPS bijels have only been formed with silica nanoparticles of low surface charge densities, limiting their potential applications in catalysis and fluid transport. Here, we show how strongly charged silica nanoparticles can stabilize bijels. To this end, we carry out a systematic study employing dynamic light scattering, zeta potential, acid/base titrations, turbidimetry, surface tension, and confocal microscopy. We find that moderating the adsorption of oppositely charged surfactants on the particles is crucial to facilitate particle dispersibility in the bijel casting mixture and bijel stabilization. Our results potentially introduce a general understanding for bijel fabrication with different inorganic nanoparticle materials of variable charge density.

The visible light-driven purification of aqueous pollutants after oil/water separation was demonstrated and the relationship between the surface morphologies of meshes and the viscosities of oils for effective separation was investigated.

This chapter introduces the formation of bijels via solvent transfer-induced phase separation (STrIPS). STrIPS bijels are generated by triggering spinodal decomposition of a ternary liquid mixture composed of oil, water, solvent and surface-active nanoparticles. Bicontinuous oil/water channel networks are stabilized by interfacial jamming of the nanoparticles. Continuous production of STrIPS bijel fibers, planar films and microparticles is realized via a scalable route amenable to mass production. STrIPS bijels have asymmetric internal structures, with small domains on the surface and larger internal domains. We discuss the dependency of STrIPS bijel domain organization and size based on variation of nanoparticle concentration and surface functionalization. Moreover, we introduce a microfluidic technique to measure the fracture strength of STrIPS bijels. Mechanical reinforcement of STrIPS bijels is realized by interfacial nanoparticle cross-linking and sol–gel chemistry. Furthermore, applications of STrIPS bijels in reactive separations and as nanocomposite ultrafiltration membranes are introduced. The chapter concludes with an outlook and future perspectives on fundamental research, as well as applications for STrIPS bijels.