Solvent transfer-induced phase separation to tailor bijel fiber properties

Bicontinuous interfacially jammed emulsions (bijels) are novel soft materials that consist of two interwoven pore networks, each containing a liquid that is immiscible with the other.  The interface is stabilized by nanoparticles, providing high interfacial surface areas and robust mechanical properties.  Bijels have been limited to a small number of compatible oils and hydrophilic liquids.  Allowing reactants in the aqueous phase and products in the oil phase would create a continuous reactor, surpassing intrinsic limitations of emulsion microreactors.

Researchers in the Stebe and Lee labs have designed a method based on solvent transfer-induced phase separation (STRIPS) to continuously generate asymmetric and hierarchical bijels. Using ternary liquid-liquid phase separation with a liquid architecture expands the possibilities of colloidal emulsions that can be generated. Phase separation is induced by extraction of a solvent from a homogeneous ternary mixture. The technique uses a rapid injection of a homogeneous mixture of three liquids into a continuous phase, with ethanol as a solvent to allow homogeneous mixing of the other two immiscible liquids. Exposing the liquid fiber to UV light polymerizes the material, with the internal structure tuned by the nanoparticle concentration.  Multiple length scales can be accommodated for size-selective transport and separations.

• High interfacial surface areas
• Compatible with wide range of materials
• Size-selective
• Control overall bijel shape
• Continuous reactor

• Filtration membranes to separate out pollutants, viruses, and bacteria from contaminated water
• Emulsions for food and cosmetics
• Fog harvesting for drinking water, crop irrigation, and forest restoration
• Fiber scaffolds for tissue engineering
• Catalytically active particles on surfaces
• Continuous chemical reactions
• Refining biofuels