Controlling Interfacial Composition, Coverage and Mechanics for Stable Capsule Formation

Nanoparticle-surfactant mixtures can form stable fluid interfaces with large dilatational modulus. Surfactants modify the nanoparticle hydrophobicity and therefore tune the wettability of the nanoparticle to nearby interfaces. Adsorption timescales of the nanoparticle-surfactant complexes to interfaces are controlled by diffusion. These diffusion timescales are comparable to residence times in microfluidic devices, allowing the interfacial coverage on monodisperse droplets and bubbles to be controlled. For confined bubbles translating in a long microchannel, sufficiently long residence times lead to the formation of extremely stable gas-filled capsules. In this talk we vary the dispersion composition to vary the particle hydrophobicity and adsorption to interfaces. We examine the role of dispersion composition on capsule formation, and independently probe the interfacial mechanics at similar surface coverages and compositions using a custom built microtensiometer.