Designing Colloidosomes with Unjammed Interfaces

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Emulsions consist of liquid droplets that are suspended in a second, immiscible liquid, such as oil droplets in water. Pickering emulsions are a special kind of emulsion in which the small particles sit at the interface between the droplets and the surrounding liquid. The presence of these small particles at the droplet interface ensures that the droplets do not coalesce with each other and break the emulsion. These emulsions are commonly found in commercial cosmetics, foodstuffs, and in newer applications like 3D printing. Typically, the interface of a droplet is nearly completely covered with particles, which stops coalescence by essentially by creating armor around the droplet. However, coating the droplets completely requires a large number of small particles, which poses an environmental challenge, and it limits the ability to make emulsions with novel properties. To address these issues, this project will study how combinations of particles with different surface properties can create interfaces that prevent coalescence at lower particle concentrations. The research will examine the relationship between the properties of the interface and the behavior of individual drops and collections of drops to determine the best optimal interface configuration to stabilize emulsions. Additionally, the research team will develop several traveling labs for high schools in the region surrounding Texas Tech University that will educate students about the science behind common many commercial products.Currently, particle interfaces on colloidosomes primarily impact droplet behavior due to interfacial jamming. The hypothesis underlying this project is that colloidosomes’ behavior can be modified by creating unjammed interfaces with high interfacial viscoelasticity using particles with bidispersity of charge or wettability. A series of experiments that combine interfacial rheology, microfluidics, and image analysis will be conducted to examine this hypothesis. To start, the project will characterize rheology and microstructure of a range of highly viscoelastic, moderate surface coverage interfaces. Then, these interfaces will be replicated on colloidosomes using microfluidic techniques. The resultant colloidosomes will be forced to deform, breakup, and coalesce using specific microfluidic geometries. The properties of the colloidosomes will be compared to interfacial rheology measurements, drops with simple liquid and/or jammed interfaces, and to theoretical predictions. The resulting data set will characterize behavior of unjammed colloidosomes and their potential utility. Creating colloidosomes with controllable interfaces will establish how interfacial elasticity and yield of unjammed particle interfaces affects colloidosome behavior, increasing the capability to manipulate colloidosome systems for important applications.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.