Non-Contact Mechanics of Soft and Liquid Interfaces by Hydrodynamic Confinement Using a Frequency-Modulated AFM

Lucie Corral, Christian Curtil, Medhi Lagaize, Marc Leonetti, and Hubert R. Klein

Published in Langmuir :

https://doi.org/10.1021/acs.langmuir.6c01228

Measuring the mechanical response of liquid interfaces without direct contact remains a major experimental challenge. Here, we present a frequency-modulation atomic force microscopy (FM-AFM) method to probe liquid interfaces through the hydrodynamic confinement of a viscous liquid film between an oscillating probe and the interface. This approach provides simultaneous access to the elastic and dissipative components of the effective mechanical response under confinement. It is applied to a liquid−liquid interface, which exhibits a predominantly viscous response with a finite elastic contribution and a confinement thickness in the micrometric range. These results show that hydrodynamic confinement provides a sensitive, noncontact approach to compare the mechanical responses of soft and liquid interfaces, and opens perspectives for investigating complex and highly deformable systems such as polymer films, biological membranes, and rafts of nanoparticles.