PhD defence: Particle-stabilized bicontinuous emulsions Silica nanoparticle functionalization and electroosmotic flow

Just like the capillaries and renal tubules in your kidneys, particle-stabilized bicontinuous emulsions (also known as bijels) consist of two complexly intertwined, but separate fluid networks with a large liquid-liquid surface area available for molecular exchange. While the fluid network in the kidney is stabilized by the lining kidney cells, the oil and water networks of bijels are stabilized by a jammed layer of nanoparticles. We can synthesize bijels by inducing de-mixing of a precursor through solvent transfer-induced phase separation (STrIPS). When surface-active nanoparticles are included, irreversible attachment quickly stabilizes the interface, freezing the structure and preserving smaller pores.

In this thesis, we investigate the synthesis and use of particle-stabilized bicontinuous emulsions (bijels), exploring new methods to enhance their stability and functionality. We delve into the synthesis and characterization of neutrally wetting particles that can stabilize bicontinuous emulsions. Next, the development of a single-channel microfluidics technique allows the rapid synthesis of bijel fibers. The centimeter-long fibers have a diameter of 50 micrometers, containing a web of fluid tunnels only a micrometer wide! More complex co-flow microfluidics, in combination with a custom-built printer, allow us to print thousands of bijel fibers parallel to each other, forming the basis for a bicontinuous microreactor.

Finally, we work towards fulfilling a longstanding promise of bicontinuous emulsions: continuous biphasic catalysis. Without a way to pump water through the water pore network, diffusion limitations hinder the device from reaching its full potential. We show for the first time that liquids can be pumped through the fluid bicontinuous gels via electroosmosis.