Sessile-drop-induced bending of atomic force microscope cantilevers: a model system for monitoring microdrop evaporation

Abstract

To monitor the evaporation kinetics of drops from solid surfaces, and to investigate the interaction between liquids and solids, microscopic drops of liquids were deposited onto atomic force microscope cantilevers. Due to the surface tension of the liquid, the Laplace pressure inside the drop, and the change of the interfacial stress at the solid–liquid boundary, the cantilever bends and is deflected by typically a few hundred nanometers. We used liquids with different vapour pressures and surface tensions, in order to vary the evaporation time and also the magnitude of the surface forces exerted by the drops. For fast evaporating drops the cantilever bending along the longitudinal axis was measured versus time. In the case of non-evaporating drops the overall bending was recorded with optical methods. We developed a FEM model for cantilever bending as an improvement to a previously presented analytical model. FEM simulations are confirmed by experimental results.