Correlation between shear near-field acoustic emission and the radius of curvature of a water bridge meniscus formed between parallel plates

Sotelo C.E.; Reyes D.F.; Bringas R.E.; Supichayanggoon K.; Solano C.J.; La Rosa A.H. · Journal of Physics: Conference Series (2025) · DOI: 10.1088/1742-6596/3052/1/012001

Resumen

A water bridge, formed through capillary condensation at the nanometer-sized gap defined by a sharp probe and a flat sample, produces acoustic emission when subjected to shear motion. Very recently, it has been found that such an emission is sensitively detected in the near-field zone by the Shear-force Near-field Acoustic Microscope (SANM). When additionally subjected to vertical elongation and compression, reports from experiments performed in an AFM set up and complemented with a corresponding hydrodynamic model, indicate that the meniscus remains in mechanical equilibrium (but not in thermodynamic equilibrium) while maintaining its volume constant. Herein, we present numerical solutions of the hydrodynamic equation governing the profile of the meniscus formed between two parallel plates, and verify calculations previously reported for similar confining geometries. Significantly new, we find a correlation between the acoustic emission obtained in SANM experiments and the inverse of the meniscus' total radius of curvature at different gap distances between the plates. While the fitting may not be universal (as the experiment depends on different parameters) the trend of agreement between the model and experimental results is encouraging. These measurements are relevant to investigations on the dynamic behavior of fluids near hydrophobic/hydrophilic substrates, wetting properties of solids, and nanotribology phenomena in general. © Published under licence by IOP Publishing Ltd.

Instituciones: Universidad Nacional Mayor de San Marcos; Universidad Nacional de Ingeniería