New light on molecular attraction
Whether a surface is
hydrophobic or hydrophilic is determined by the degree of molecular attraction
between the substrate and the liquid.
Controlling the attraction is key to the wettability of substrates, which determines how many physical and biological systems function. For instance, plant leaves are often hydrophobic, allowing them to remain dry during rain so that gas exchange can occur through their pores. However, liquids such as paints, inks and lubricants are required to spread out to coat or 'wet' surfaces.
Researchers at University of Bristol from the School of Physics applied a number of theoretical and simulation techniques and discovered rich and unexpected behaviour such as divergent density fluctuations associated with the phenomenon of 'critical drying' at a superhydrophobic substrate.
They provide a firm conceptual framework for tailoring the properties of new materials, including finding super-repellant substrates, such as expelling water from windscreens. Their findings are published in the Proceedings of the National Academy of Sciences (PNAS).