Interface Forces Leak Through Graphene Coatings
Graphene, a single layer of carbon atoms arranged in a honeycomb lattice, is one of the most widely studied 2D materials. Coating solid-state substrates with graphene can alter their surface properties, such as friction and adhesion. Whereas graphene is nearly and conspicuously transparent to visible light, it may also diminish—or “screen”—the weak, short-range forces known as van der Waals (vdW) interactions. But the strength of the effect has been under debate. Now Zhaohe Dai at Peking University and his colleagues have clarified the picture, reporting a transparency—or lack of screening—of up to 85% via both experiments and theory [1]. Their results overturn previous studies, which suggested that graphene almost completely screens vdW interactions.
Dai and his colleagues used an atomic force microscope with a custom-made colloidal sphere as its probe. Thanks to the probe’s well-defined geometry, they could obtain more precise and consistent results compared with earlier studies with irregular probes. By measuring the interface forces as the probe approached the graphene, the researchers inferred that one to five layers of graphene can screen 15% to 50% of the vdW interactions. Intriguingly, they also discovered that detaching an object from an unsupported graphene layer required more energy than from a substrate-supported one. The results are consistent with theoretical calculations, revealing that vdW interactions are not a simple sum of graphene and substrate contributions but instead a combination of more complex contact mechanics and many-body effects.
Dai says that this study clarifies and deepens the understanding of how vdW interactions in layered materials combine. “It will guide the design of new 2D-material-based nanomechanical systems,” he adds.
–Tianhan Liu
Tianhan Liu is an Associate Editor of Physical Review Letters and Physical Review Materials.
References
- C. Yu et al., “Transparency of graphene to solid-solid van der Waals interactions,” Phys. Rev. Lett. 135, 156202 (2025).