(440a) Studying Fluid-Fluid Interfaces with a Custom Sub-Phase Exchange Microscopy Cell

Microscopy investigations of molecular films at fluid-fluid interfaces are challenging to perform when changes to the chemistry of the surrounding bulk-phases are either required, or important. In-situ changes to bulk-phase chemistry can be intended to mimic processing or biological changes that can influence film stability in emulsions, phospholipid films, or foams. There are many materials with properties that depend on the structure of interfacial films within the bulk material itself, including oil-water emulsions in food and petroleum applications, hydrate plugs in the oil and gas industry, and even biological materials where phospholipid mono- and bilayers are present. Altering bulk chemistry can influence film structure, and this in turn can change bulk properties, but studying such processes experimentally is not trivial. We developed a sub-phase exchange cell that we have tested experimentally and simulated in COMSOL Multiphysics to determine the operating conditions that will yield desired concentration changes in the bulk sub-phase. The presentation will include the design of the sub-phase exchange cell, the results of the simulations, and a discussion of our work transferring monolayer graphene from a copper film to an air-water interface by exchanging a water sub-phase with ammonium persulfate. The results will include an analysis of the observed interactions of model 2D graphene particles at an air-water interface.