Miscible antifoams: Leveraging evaporative solutocapillary flows for a novel antifoam mechanism

Foaming is often problematic in non-aqueous fuels and lubricating oils, leading to the use of additives called antifoams. Existing antifoams are solid particles or immiscible liquid droplets requiring specialized high shear machinery for incorporation. These antifoams are prone to gravitational separation, or removal under dynamic operation conditions – rendering them ineffective. A miscible liquid that is effective as an antifoam would overcome these obstacles. 

Evaporation greatly influences thin film stability, stabilizing or destabilizing depending on the volatility and surface tension of liquid components. A fluid with higher surface tension and higher volatility destabilizes a thin film as it evaporates. We hypothesize that such a fluid would act as a miscible antifoam, leveraging evaporation driven solutocapillary flows. We test this utilizing a custom experimental platform that probes thin film dynamics and foam stability at the single bubble level. We investigate several potential miscible antifoam systems with a range of surface tension deficits and viscosity ratios. With performance equivalent to or better than conventional and the added benefit of ease of use, miscible antifoams are have the potential to be groundbreaking.