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Coalescence of Sessile Drops on PDMS Surfaces |
Knowledge
of the dynamical behavior of droplets on a surface
is important in numerous technological processes
including spray cooling, ink-jet printing, and
solder jet technology. Despite its importance,
very few studies have focused on the dynamics of
coalescence, or merging, of two drops spreading
on a surface. In the Anna group, we have
developed a novel method of controlling the merging
of drops on a surface by using a microfluidic device
to inject volume into two approaching sessile drops
at a controlled rate and separation. We simultaneously
acquire high-speed images of the side and top views
of the coalescence event through use of a prism.
Using this apparatus, our preliminary experiments
have shown that the dynamics of coalescence are
very different depending on the wetting properties
of the solid surface. Existing scaling arguments
and theoretical arguments do not capture the observed
behavior. In this research project, the undergraduate
student will investigate this new behavior by performing
surface coalescence experiments and examining the
influence of substrate wettability, driving flow
rates, viscosity, and other experimental parameters
on the dynamics. |
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