Though relatively unknown, wettability is one of the most important properties that researchers need to assess in a variety of chemical and physical processes. This is the property that solid materials have, which dictate how water and other liquids will behave on them. Some may retain water, while others may force the liquid to aggregate in droplets, and remain on the surface. Others may still be repellent, as in hydrophobic, and force liquids away from them. Assessing the degree of wettability has until now been plagued by poor-resolution techniques, but all that changed thanks to a recent innovation.
Researchers at the Massachusetts Institute of Technology (MIT) look at the old measurement technique – which only involved measuring the shape of the droplets – and decided to improve on it. And improve they did, about 10,000 times over. Their new method of assessing wettability is incredibly precise, providing an unprecedented level of detail in this type of studies. The interaction of solids and liquids can now be determined with amazing resolution, even if the solid surfaces used in the study are curved, textured, or have other complex shapes. This was impossible with the previous method.
“This is something that was unthinkable before. It allows us to make a map of the wetting,” explains the MIT Paul M. Cook Career Development associate professor of materials science and engineering, Francesco Stellacci. He was also the leader of the group that was in charge of producing the new, high-resolution measurement technique. To get a better idea of how precise the method is, imagine that it can show the interactions between solids and liquids down to the level of individual molecules and atoms. Additional details of the innovation appear in the April 25 issue of the journal Nature Nanotechnology.
The researchers managed to obtain such amazing results by taking an atomic force microscope (AFM), and reprogramming its controls. The instrument – in its basic configuration – uses a small tip as a cantilever for analyzing materials down to atomic resolution. Generally, the cantilever vibrates over distances of several tens to hundreds of nanometers when touching a sample, but the MIT team managed to constrain its oscillations to only a few nanometers. “By doing so, you actually improve the resolution of the AFM,” Stellacci adds. The work was supported by the Swiss National Science Foundation and the Packard Foundation, ScienceDaily