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The stretching of viscoelastic polymer solutions close to break-up can create attached drops on a filament, whose properties and dynamics are little understood. The stretching of capillary bridges and the consecutive filament, until its breakup, can be quantified using diameter-spacetime diagrams, which demonstrate hierarchy, as well as, asymmetry of satellite drops around a big central drop. All drops experience migration, oscillation and merging. In addition, the position of the minimum diameter on the filament is determined, along with the number of drops, their positions, the diameters of drops and the filament breakup time. The maximum number of drops on the filament can be predicted using the Deborah number. The diagrams also quantify the large Hencky strains in the filaments before pinch-off. The obtained minimum diameter is used to measure the extensional viscosity, which indicates the effect of polymer concentration and direction of filament thinning.

We derive a model to describe the dynamics of confined directional drying of a colloidal dispersion. In such experiments, a dispersion of rigid colloids is confined in a capillary tube...

Viscoelastic liquid transfer from one surface to another is a process that finds applications in many technologies, primarily in printing. Here, cylindrical-shaped capillary bridges pinned between two parallel disks are considered. Specifically, the effects of polymer mass fraction, solution viscosity, disk diameter, initial aspect ratio, final aspect ratio, stretching velocity, and filling fraction (alike contact angle) are experimentally investigated in uniaxial extensional flow. Both Newtonian and viscoelastic polymer solutions are prepared using polyethylene glycol and polyethylene oxide, with a wide variety of mass fractions. The results show that the increase in polymer mass fraction and solvent viscosity reduces the liquid transfer to the top surface. Moreover, the increase in the initial and final stretching heights of the capillary bridge also decreases the liquid transfer for both Newtonian and viscoelastic solutions. Finally, the shape of the capillary bridge is varied by changing the liquid volume. Now, Newtonian and viscoelastic solutions exhibit opposite behaviors for the liquid transfer. These findings are discussed in terms of interfacial shape instability and gravitational drainage.

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