26 research outputs found
Drop spreading and gelation of thermoresponsive polymers
Spreading and solidification of liquid droplets are elementary processes of
relevance for additive manufacturing. Here we investigate the effect of heat
transfer on spreading of a thermoresponsive solution (Pluronic F127) that
undergoes a sol-gel transition above a critical temperature . By
controlling the concentration of Pluronic F127 we systematically vary ,
while also imposing a broad range of temperatures of the solid and the liquid.
We subsequently monitor the spreading dynamics over several orders of magnitude
in time and determine when solidification stops the spreading. It is found that
the main parameter is the difference between the substrate temperature and
, pointing to a local mechanism for arrest near the contact line.
Unexpectedly, the spreading is also found to stop below the gelation
temparature, which we attribute to a local enhancement in polymer concentration
due to evaporation near the contact line.Comment: 9 pages, 10 figure
Solidification of liquid metal drops during impact
Hot liquid metal drops impacting onto a cold substrate solidify during their
subsequent spreading. Here we experimentally study the influence of
solidification on the outcome of an impact event. Liquid tin drops are impacted
onto sapphire substrates of varying temperature. The impact is visualised both
from the side and from below, which provides a unique view on the
solidification process. During spreading an intriguing pattern of radial
ligaments rapidly solidifies from the centre of the drop. This pattern
determines the late-time morphology of the splat. A quantitative analysis of
the drop spreading and ligament formation is supported by scaling arguments.
Finally, a phase diagram for drop bouncing, deposition and splashing as a
function of substrate temperature and impact velocity is provided
Influence of cationic composition and pH on the formation of metal stearates at oil-water interfaces
Folding Films, Inverse Coarsening, and the Bubble-Bursting Cascade
International audienceBubble rupture is one of the principle mechanisms in which foams are assumed to coarsen, creating a smaller population of larger bubbles over time. Here, however, we demonstrate that for a large range of situations bubbles that rupture on an interface 'inverse coarsen', leading to a larger population of smaller bubbles. We present high speed images and numerical simulations to demonstrate that when a bubble bursts the retracting film can fold and entrap air. The folding leads to a torus of entrapped air which breaks up into a ring of daughter bubbles. These results have broad implications for any process involving bubbles on an interface, including air-water transfer and interfacial foam coarsening