Correlation of nanoscale behaviour of forces and macroscale surface wettability

Abstract

In this manuscript, we demonstrate a method based on atomic force microscopy which enables local probing of surface wettability. The maximum pull-off force, obtained from force spectroscopy shows a remarkable correlation with the macroscopically observed water contact angle, measured over a wide variety of surfaces starting from hydrophilic, all the way through to hydrophobic ones. This relationship, consequently, facilitates the establishment of a universal behaviour. The adhesion forces scale with the polar component of surface energy. However, no such relation could be established with the dispersive component. Hence, we postulate that the force(s) which enable us to correlate the force spectroscopy data measured on the nanoscale to the macroscopic contact angle are primarily arising from electrostatic-dipole-dipole interactions at the solid-liquid interface. London forces play less of a role. This effect in is line with density functional theory (DFT) calculations suggesting a higher degree of hydroxylation of hydrophilic surfaces. This result shows that molecular simulations and measurements on an atomic scale can be extrapolated to macroscopic surface wetting problems.

Water wettability of graphene: interplay between the interfacial water structure and the electronic structure

“…Indeed, this correlation has been demonstrated experimentally over a wide variety of surfaces. 74 The DFT-simulated AFM energy proles are shown in the main panel of Fig. 5b (see Methods for technical details).…”

Mapping micrometer-scale wetting properties of superhydrophobic surfaces

“…Since its invention in 1986, Atomic Force Microscopy (AFM) has become a standard and powerful surface characterization tool [18]. AFM was used to characterize surface wetting properties by measuring the tip-surface interactions [19][20][21][22]; however, the AFM tip is typically made of solid silicon/silicon nitride and has a pyramidal geometry, which poorly approximates droplet-surface interactions.…”

Nature of Lone-Pair–Surface Bonds and Their Scaling Relations

“…We explain the role of formal charges, geometry, and surface electronic and mechanical properties on the BEs. Such knowledge can then be used to predict the water interaction with a wide range of surfaces and has applications in electrocatalysis and electrochemistry, − surface wetting, − solid–water interfaces beyond TMs, − solids corrosion, ,, biological systems, , etc. As a consequence of the material-independent scaling relations we find between the N and O 2p lone-pair species, such knowledge is transferrable to other molecules in this class.…”