Lecturer: Dr. John Kolinski
Affiliation: Racah Institute of Physics,
The Hebrew University of Jerusalem
Abstract:
Before a falling drop can contact a solid surface,
it must displace the air beneath it. In the
classical paradigm of droplet impact, the liquid
droplet initially contacts the surface at a point
centered on the impact axis, and spreads
outward to wet the surface; however, this picture
completely ignores the surrounding air. Recent
calculations and experiments show that as the
falling drop pierces through the air, the air fails
to drain, and compresses. These dynamics take
place at fleeting timescales and diminutive
lengthscales, and are obscured by the bulk of the
drop, making experimental observation difficult.
Using a novel implementation of TIR
microscopy to directly image the dynamics of
the liquid-air interface, we show that the liquid
skates over a nanometer thin film of air, as
predicted by theoretical calculations; we further
probe the stability of the air film, and report the
surprising observation that the droplet can
completely rebound from the solid surface at
low impact velocities. Finally, we address the
first moments of liquid-solid contact with a
study of the dynamics at the advancing liquid-
solid contact line.