Chemical engineers at the University of Illinois Chicago and UCLA used the U.S. Department of Energy’s Advanced Photon Source (APS) in answering longstanding questions about the underlying processes that determine the life cycle of liquid foams. The breakthrough in understanding how liquid foams dissipate could help improve the commercial production and application of foams in a broad range of industries and could lead to improved products. Findings of the research were featured in the Proceedings of the National Academy of Sciences of the United States of America.
Foams are a familiar phenomenon in everyday lives — mixing soaps and detergents into water when doing dishes, blowing bubbles out of soapy water toys, sipping the foam off a cup of lattes or milk shake. Liquid foams can occur in a variety of natural and artificial settings. While some foams are produced naturally, as in bodies of water creating large ocean blooms on the beaches, others arise in industrial processes. In oil recovery and fermentation, for example, foams are a byproduct.
Whenever soapy water is agitated, foams are formed. They are mostly gas pockets separated by thin liquid films that often contain tiny molecular aggregates called micelles. Oily dirt, for example, is washed away by hiding in the water-phobic cores of micelles. In addition, fat digestion in our bodies relies on the role of micelles formed by bile salts.
Over time, foams dissipate as liquid within the thin films is squeezed out. Soap and detergent molecules that are by very nature amphiphilic (hydrophilic and hydrophobic) aggregate within water to form spherical micelles, with their outward-facing heads being hydrophilic and water-phobic tails forming the core.
Read more on the ANL website
Image: Micellar foam films show grayscale intensity variations that correspond to rich nanoscopic topography mapped using IDIOM protocols.
Credit: Chrystian Ochoa and Vivek Sharma/UIC