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It is well known that using nanostructured coatings on the substrate surface, such as nanofiber mats, can improve heat transfer rate during a drop impact onto a hot substrate. This is primarily due to liquids penetrating the pores of the coating. Also, in contrast to smooth surfaces, rebounding or splashing can be avoided after drop impact on nanostructured coatings, and the hydrodynamics of droplet spreading can also be significantly influenced.

The goal of this project is to investigate the mechanisms of droplet spreading, imbibition into porous structures, and evaporation during drop impact on substrates with porous coatings, both experimentally and theoretically. The influence of fluid properties, coating morphology, and ambient conditions on these processes need to be explored. The experimental study involves drop impact experiments in an air-conditioned test cell. Heatable substrates are used, which are coated with nanofibers. With the electrospinning process, nanofiber mats can be made of different polymers and with variable parameters, e.g. fiber diameter and mat thickness. In order to understand the influence of fluid properties, pure liquids as well as binary mixtures are used. Furthermore, the deposition behavior of particles in porous coatings is investigated by using (nano-) suspensions.

The theoretical investigation aims at the understanding of each processes separately and the relationship among each other.

CRC 1194 – Interaction between Transport and Wetting Processes, Project A04