Atomic-Scale Visualisation of Interfacial Water Structure and Electrical Behaviour

At a solid-liquid interface (SLI), liquid molecules arrange into quasi-discrete layers extending a few molecular diameters from the surface due to surface-molecule interactions and confinement (1). These interfacial layers influence adhesion, wetting, ion solvation and transport, and (bio)chemical processes (2). Directly probing this structuring and its physical properties remains challenging, as it requires atomic-scale resolution in both the vertical and lateral directions. Techniques including vibrational spectroscopy, the Surface Force Apparatus, and the Atomic Force Microscope (AFM) have been used to probe these effects, with AFM uniquely offering atomic-scale resolution in both dimensions. Here I will present two complementary approaches based on AFM used to study the physical properties of liquid structuring at interfaces with solid 2D crystals and soft biomolecules. One probes liquids under nanoconfinement in 2D-material nanoenclosures (3, 4), while the other uses 3D AFM to image interfacial liquid structure directly with atomic resolution (5–7). Together, these methods reveal interfacial water layers whose electrical response differ markedly from bulk water, offering new insight into natural processes and providing important information for theories of liquid-mediated interactions.
 
References
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3. L. Fumagalli et al., Science. 360, 1339–1342 (2018).
4. R. Wang et al., Nature. 646, 606–610 (2025).
5. S. Benaglia et al., Phys. Rev. Lett. 127, 196101 (2021).
6. S. Benaglia, H. Read, L. Fumagalli, Faraday Discuss. 249, 453–468 (2024).
7. S. Benaglia, S. Chiodini, J. Colloid Interface Sci. 685, 342–349 (2025).