Bijel Membranes with Tunable Porosity for pH-responsive Microfiltration.

Bicontinuous interfacially jammed emulsion gels (bijels) are nanoparticle-stabilized composite materials with significant potential in membrane separations. This work introduces the fabrication of bijel sheets with symmetric pore structures and demonstrates their use as pH-responsive microfiltration membranes. Unlike established hollow fiber-bijel membranes, symmetric bijel sheets offer a more scalable and robust production route of separation membranes via roll-to-roll solvent transfer induced phase separation (R2R-STrIPS). The role of substrate wetting by the liquid bijel precursor in determining membrane structure is analyzed. Pore sizes are tuned by varying the surfactant concentration in the precursor solution. In contrast to existing bijel membranes that rely on rigid polymer scaffolds - resulting in brittleness and limited control over separation properties, stimuli-responsive polymers are employed to create soft, adaptable bijels. This pH-responsiveness enables dynamic control over membrane permeability, including feed-stream-driven compaction and tunable performance via polymer cross-linking. These functional characteristics expand the potential applications of symmetric bijel sheets to drug delivery, controlled release, and soft robotics.