The project is concerned with foams and emulsions, which appear in many edible food products, such as salad dressing and ice cream, as well as consumer and personal care products, such as shaving creams, cosmetics, and detergents. In addition, they are central to many technologies and industries like distillation, oil recovery, and removal of pollutants from environmental media. In many of these products and processes, microstructure and stabilization of foams and emulsions play critical roles in determining their properties and performance. However, some fundamental questions such as what the most efficient structure is in "very dry" foams and emulsions has been a long-lasting, unsolved problem for over a century. Moreover, as eco-friendly nanoparticles emerge as an alternative stabilizing agent to replace traditional surfactants, how these particles help stabilize foams and emulsions remains unclear. The project aims to answer these questions by imaging foams and emulsions at high resolution in microgravity environment in which gravity-induced influencing factors can be eliminated.
The goal of this project is to understand (a) the packing structure of monodisperse foams and emulsions close to the dry limit with zero-fraction of continuous phase and (b) the impact of using colloidal particles instead of surfactant on microstructure and stabilization of foams and emulsions. Microgravity environment is especially suitable for these studies because 1) bubbles/drops can freely assemble without being confined by a container, and 2) coalescence can be eliminated and the coarsening process can be isolated and studied. Proposed microgravity experiments include microfluidic generation of monodisperse bubbles and drops, collection of foams and emulsions, and microscopy imaging of foam/emulsion samples. The resultant microscopy images to be collected on ISS will then be analyzed and interpreted using Imaris, ImageJ, in-house Matlab program, and Surface Evolver program. The proposed experiments plus data analysis will provide important insights on understanding the long-lasting Kelvin problem regarding 3D space partition into equal volumes with the least surface area, as well as elucidate the role of particles, especially those with rough surfaces, in suppressing coarsening.
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.