The research team studied water confined by five different surfaces: mica, graphene oxide, silicon, diamond-like carbon, and graphite. The viscosity continued to increase as the surfaces were moved closer together. In research reported in the journal, this water behavior appeared only when water was confined to spaces of a few nanometers or less-the equivalent of just a few layers of water molecules. The results were scheduled to be reported September 19 in the journal Nature Communications. Research into the properties of liquids confined by different materials was sponsored by the Department of Energy's Office of Basic Sciences and the National Science Foundation. Considering that nano-confined water is ubiquitous in animal bodies, in rocks, and in nanotechnology, this new understanding could have a broad impact. Those effects could be important to designers of devices such as high resolution 3D printers that use nanoscale nozzles, nanofluidic systems and even certain biomedical devices. "Anyone performing an experiment, developing a technology or attempting to understand a biological process that involves water or another liquid at this size scale will now have to take the properties of surfaces into account." "At the nanoscale, viscosity is no longer constant, so these results help redefine our understanding of fluid flow at this scale," said Elisa Riedo, an associate professor in the School of Physics at the Georgia Institute of Technology. And it also provides a new factor that the designers of tiny mechanical systems must take into account. The effect of container properties on the fluids they hold offers yet another example of surprising phenomena at the nanoscale. Nanoscopic glass channels can make water flow more like ketchup than ordinary H2O.
A new study shows that in nanoscopic channels, the effective viscosity of water in channels made of glass can be twice as high as water in plastic channels. But at nanometer-size scales for water and potentially other fluids, whether the container is made of glass or plastic does make a significant difference.