Capillary Forces in Atomic Force Microscopy and Liquid Nanodispensing
Résumé
Capillary forces are an important issue when performing atomic force microscopy (AFM) in air. The formation of a water meniscus between the tip and the surface often leads to a deterioration of the tip or sample which may affect the spatial resolution of the instrument. The development of dynamic modes allowed decreasing these effects but artefacts due to capillary forces are still present. The presence of a small liquid bridge between the tip and the surface has also been used to locally modify the surface. Several tip-assisted lithography techniques have been developed and may find a wide range of applications in nanociences. In particular, a liquid nanodispensing technique (NADIS) using specific AFM tips allows to deposit directly on the surface liquid droplets with volumes in the femto- to attoliter range. In this chapter, we describe the effect of capillary forces on these AFM-based techniques. After a review of the influence of capillary forces in AFM in static and dynamic modes, we focus on the NADIS technique which provides a unique way to study nanomenisci with controlled size.