(660e) Towards Continuously Operated Chemical Reactions in Bicontinuous Systems: Making Robust Strips-Bijels for Microfluidic Applications

Most industrial production routes of pharmaceuticals, detergents, pesticides, polymers, and fuel products have difficulties in obtaining pure forms of their products. They generate enormous volumes of organic waste and account for 50% of industrial energy consumption.¹

Biphasic systems can be used to produce value-added chemicals, for which reactions and separations take place in a single-step without solvents. Bicontinuous interfacially jammed emulsion gels (bijels) are promising candidates for biphasic chemical reactions due to their unique structural features.² Bijels are composed of an interpenetrating bicontinuous fluid network, stabilized by a jammed layer of colloidal particles at their interface.^3,4 The bicontinuous structure can transport chemical species through the two liquid phases, whilst the nanoparticle-laden semi-permeable interface regulates the transport between both phases.

Herein, we research bijel fibers produced by solvent transfer induced phase separation (STRIPS) bijels⁴ and harness their unique structural properties and post-processing capabilities for microfluidic applications. Using confocal laser scanning and scanning electron microscopy, we investigate bijel structures in dependence of their fabrication parameters. We find that the wetting properties and colloidal stabilities of the nanoparticles influence the phase separation behavior during bijel formation, enabling precise control over the bicontinuous domain sizes. Moreover, the ternary liquid phase behavior controls bijel morphology, enabling the formation of bijels with tailored architectures. Post processing by reinforcement of the interfacially jammed nanoparticle scaffold results in robust STRIPS bijels with potentials for convective flows. Controlling structural and mechanical properties of STRIPS bijels enables us to use them for biphasic mass transfer. Also, robust STRIPS bijels can be readily fabricated with diverse functional nanoparticles as well as a wide variety of oil/solvent combinations, leading to tailored architectures and mechanical properties for potential applications as catalytic membrane reactors.

References:
1. Sholl, D. S., & Lively, R. P. (2016). Seven chemical separations: to change the world: purifying mixtures without using heat would lower global energy use, emissions and pollution--and open up new routes to resources. Nature, 532(7600), 435-438.
2. Stratford, K., Adhikari, R., Pagonabarraga, I., Desplat, J. C., & Cates, M. E. (2005). Colloidal jamming at interfaces: A route to fluid-bicontinuous gels. Science, 309(5744), 2198-2201.
3. Herzig, E. M., White, K. A., Schofield, A. B., Poon, W. C. K., & Clegg, P. S. (2007). Bicontinuous emulsions stabilized solely by colloidal particles. Nature materials, 6(12), 966.
4. Haase, M. F., Stebe, K. J., & Lee, D. (2015). Continuous fabrication of hierarchical and asymmetric bijel microparticles, fibers, and membranes by solvent transfer‐induced phase separation (STRIPS). Advanced Materials, 27(44), 7065-7071.