  This work presents a combined experimental and theoretical study of dynamic
contact angle hysteresis using liquid bridges under cyclic compression and
stretching between two identical plates. Under various loading rates, contact
angle hysteresis for three different liquids was measured by examination of
advancing and receding angles in liquid bridges, and the capillary forces were
recorded. It is found that, for a given liquid, the hysteretic phenomenon of
the contact angle is more pronounced at higher loading rates. By unifying the
behaviour of the three liquids, power-law correlations were proposed to
describe the relationship between the dynamic contact angle and the capillary
number for advancing and receding cases. It is found that the exponents of
obtained power-law correlations differ from those derived through earlier
methods (e.g., capillary rise), due to the different kinematics of the
triple-line. The various hysteretic loops of capillary force in liquid bridges
under varied cyclic loading rates were also observed, which can be captured
quantitatively by the prediction of our developed model incorporating the
dynamic contact angle hysteresis. These results illustrate the importance of
varying triple-line geometries during dynamic wetting and dewetting processes,
and warrant an improved modelling approach for higher level phenomena involving
these processes, e.g., multiphase flow in porous media and liquid transfer
between surfaces with moving contact lines.

Soft Condensed Matter