title: Shape and Effective Spring Constant of Liquid Interfaces Probed at the Nanometer Scale: Finite Size Effects.
abstract: We investigate the shape and mechanical properties of liquid interfaces down to nanometer scale by atomic force microscopy (AFM) and scanning electron microscopy (SEM) combined with in situ micromanipulation techniques. In both cases, the interface is probed with a cylindrical nanofiber with radius R of the order of 25-100 nm. The effective spring constant of the nanomeniscus oscillated around its equilibrium position is determined by static and frequency-modulation (FM) AFM modes. In the case of an unbounded meniscus, we find that the effective spring constant k is proportional to the surface tension γ of the liquid through k = (0.51 ± 0.06)γ, regardless of the excitation frequency from quasi-static up to 450 kHz. A model based on the equilibrium shape of the meniscus reproduces well the experimental data. Electron microscopy allowed to visualize the meniscus profile around the fiber with a lateral resolution of the order of 10 nm and confirmed its catenary shape. The influence of a lateral confinement of the interface is also investigated. We showed that the lateral extension L of the meniscus influences the effective spring constant following a logarithmic evolution k ∼ 2πγ/ln(L/R) deduced from the model. This comprehensive study of liquid interface properties over more than 4 orders of magnitude in meniscus size shows that advanced FM-AFM and SEM techniques are promising tools for the investigation of mechanical properties of liquids down to nanometer scale.
authors: CEMES-CNRS , UPR 8011, 29 rue Jeanne Marvig, 31055 Toulouse, Cedex 4, France.|Université de Toulouse, 29 rue Jeanne Marvig, 31055 Toulouse, Cedex 4, France.
authors: Julien
authors: J
authors: Dupré de Baubigny
authors: Laboratoire de Physico-Chimie Théorique, CNRS UMR 7083 Gulliver, ESPCI ParisTech, PSL Research University , 10 rue Vauquelin, 75231 Paris, Cedex 5, France.
authors: Michael
authors: M
authors: Benzaquen
authors: CEMES-CNRS , UPR 8011, 29 rue Jeanne Marvig, 31055 Toulouse, Cedex 4, France.|Université de Toulouse, 29 rue Jeanne Marvig, 31055 Toulouse, Cedex 4, France.
authors: Laure
authors: L
authors: Fabié
authors: CEMES-CNRS , UPR 8011, 29 rue Jeanne Marvig, 31055 Toulouse, Cedex 4, France.
authors: Mathieu
authors: M
authors: Delmas
authors: CBMN, CNRS UMR 5248 , 2 rue Escarpit, 33600 Pessac, France.
authors: Jean-Pierre
authors: JP
authors: Aimé
authors: CEMES-CNRS , UPR 8011, 29 rue Jeanne Marvig, 31055 Toulouse, Cedex 4, France.
authors: Marc
authors: M
authors: Legros
authors: CEMES-CNRS , UPR 8011, 29 rue Jeanne Marvig, 31055 Toulouse, Cedex 4, France.
authors: Thierry
authors: T
authors: Ondarçuhu