The blistering of a viscoelastic filament of a droplet of saliva
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Wagner, Christian; Eggers, Jens; Sattler, Rainer
A fluid dynamics video of the break up of a droplet of saliva is shown. First a viscoelastic filament is formed and than the blistering of this filament is shown. Finally, a flow induced phase separation takes place nanometer sized solid fiber remains that consist out of the biopolymers.
First, the video shows the shadowgraph of a break-up of a capillary bridge of a droplet of saliva from a healthy donor. The droplet is placed between two steel plates that are gently drawn apart until the capillary bridge becomes unstable. The videos are rotated 90 degree to the right. In the first part an overview is given which shows the formation of an elastic filament that blisters finally into a series of beads. The formation of the filament is related to the high elongational viscosity of saliva which originates from the polymeric biopolymers. Second it is shown that on the highly stretched filament a Rayleigh-Plateau like instability can grow. The third part shows the final rupture of the filament. Apparently, the thin filaments that connect the remaining beads have a very high bending modulus. If they are captured on a metallic carrier it is possible tho show that they consist out of polymers, only, which is shown in the fourth part of the movie.
droplet; viscoelasticity; Non-Newtonian; Biofluids; free surface flow