Drop Impact of suspensions of fibers on a solid surface

The impact and spreading of drops of particulate suspensions on solid surfaces is relevant in various industrial applications such as in inkjet printing, or spray coating tablets in the pharmaceutical industry. The capillary dynamics of elongated particles, such as fibers, are also relevant for bioprinting cells, or fiber suspensions used for printing fiber composites. However, the role and dynamics of fiber suspensions during capillary flows remain elusive. In particular, fibers can influence the impact of a droplet, from its spreading to its fragmentation. In this study, we experimentally investigate the impact of droplets of fiber suspensions on a hydrophilic surface. We report the evolution of the spreading dynamics, film thickness, and fiber orientation as a function of the radial distance for fiber suspensions of varying mass fraction and aspect ratios. Our experiments show a substantial modification in the spreading dynamics of the drop due to the presence of fibers.