Visualisation of Small Fluid Droplets on Biological and Artificial Surfaces Using the Cryo-SEM Approach

Visualisation of small fluid droplets at a high resolution in the scanning electron microscope is a challenging task, especially if they have to be observed at the interface between two solid substrates. This report describes a Cryo-SEM approach, successfully applied for visualising droplets of various fluids, deposited on the substrates or located at the interface between two surfaces. Fragile plant trichomes, bearing glandular heads, filled (Lycopersicon) or covered with adhesive fluids (Drosera, Roridula), were also studied. In order to visualise behaviour of thin droplets at the interface, the preparation method of prints on a defined smooth metallized polymer substrate is described. The Cryo-SEM approach allows not only the visualisation of micro-droplet behaviour on various substrates, but also estimation of the contact angle of fluids. That is why it can also be applied for physico-chemical characterisation of interactions between small amounts of liquids and various biological and non-biological substrates.