Probing water for an electrifying cause
An experiment, elegant in its simplicity, helps explain why water becomes electrified when it touches hydrophobic surfaces.
For over a century, scientists have been puzzled by the electrification of water when it is brought in contact with water-repellent or “hydrophobic” materials, such as paraffin wax, oils, air bubbles and perfluorinated membranes and sheets. Underlying mechanisms remain hotly debated. Now, a team of KAUST engineers has untangled the roles of water, hydrophobicity and environmental factors in this process. This fundamental contribution could support development of better devices for microfluidics and nanofluidics and for generating clean energy.
“Hydrophobic surfaces are quite common,” notes Jamilya Nauruzbayeva, Ph.D. student and lead author of the study. “For instance, polypropylene and perfluorinated pipettes, tubes, coatings and membranes are hydrophobic surfaces used for many basic sciences and engineering applications. Thus, it is important to understand which mechanisms are at play to improve them and develop new ones.”
Himanshu Mishra, who conceived and led this study, says that he has been thinking about this problem for over five years. “Probing the surface of water is an excruciatingly difficult undertaking because the thickness of interfaces is down to the molecular scale, which no experimental techniques can probe unambiguously,” Mishra explains.