Water molecules in motion: Surprising dynamics on 2D materials

(Press-News.org) In a study published in Nature Communications, researchers from Graz University of Technology (TU Graz) and the University of Surrey tested two ultra-thin, sheet-like materials with a honeycomb structure – graphene and hexagonal boron nitride (h-BN). While graphene is electrically conductive – making it a key contender for future electronics, sensors and batteries – h-BN, often called ‘white graphite’, is a high-performance ceramic material and electrical insulator. 

Researchers found that this subtle difference completely changes how water interacts with the surfaces. Instead of jumping between fixed points as it does on graphene, individual water molecules on h-BN move in a smooth, rolling motion – almost like it is walking across.

New insights for designing surfaces This unexpected behaviour shows how even the smallest variations in a material’s atomic structure can dramatically alter how water moves at the nanoscale, offering scientists new insights for designing surfaces that control friction, wetting and ice formation. 

To capture the movement, the Graz team used a highly sensitive technique called helium spin-echo spectroscopy, which can track the motion of individual molecules without disturbing them. Researchers at Surrey also ran advanced computer simulations to model what was happening at the atomic level. 

Together, the experiments and simulations showed that water experiences less friction on h-BN – particularly when the material is supported by nickel – allowing the molecule to move more freely. On graphene, by contrast, the underlying metal strengthens the interaction between the molecule and the surface, increasing friction and making movement less smooth. 

Supporting material is critical “The support beneath the 2D material turned out to be critical – it can completely change how water behaves and even reverse what we expected,” explains Anton Tamtögl form the Institute of Experimental Physics at TU Graz. “If we can tune how water moves with the right choice of material and substrate, we could design surfaces that control wetting or resist icing. These insights could transform technologies that rely on manipulating water at the nanoscale – from advanced coatings and lubricants to desalination membranes.”

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