posted on 2022-04-22, 13:05authored byChuntian Liu, Meirong Zhao, Dunqiang Lu, Yukai Sun, Le Song, Yelong Zheng
Coalescence-induced
droplet jumping has great prospects in many applications. Nevertheless,
the applications are vastly limited by a low jumping velocity. Conventional
methods to enhance the droplet coalescence jumping velocity are enabled
by protruding structures with superhydrophobic surfaces. However,
the jumping velocity improvement is limited by the height of protruding
structures. Here, we present rationally designed limitation structures
with superhydrophobic surfaces to achieve a dimensionless jumping
velocity, Vj* ≈ 0.64. The mechanism of enhancing
the jumping velocity is demonstrated through the study of numerical
simulations and geometric parameters of limitation structures, providing
guidelines for optimized structures. Experimental and numerical results
indicate that the mechanism consists of the combined action of the
velocity vectors’ redirection and the Laplace pressure difference
within deformed droplets trapped in limitation structures. On the
basis of previous research on the mechanisms of protruding structures
and our study, we successfully exploited those mechanisms to further
improve the jumping velocity by combining the limitation structure
with the protruding structure. Experimentally, we attained a dimensionless
jumping velocity of Vj* ≈ 0.74 with an energy conversion
efficiency of η ≈ 48%, breaking the jumping velocity
limit. This work not only demonstrates a new mechanism for achieving
a high jumping velocity and energy conversion efficiency but also
sheds lights on the effect of limitation structures on coalescence
hydrodynamics and elucidates a method to further enhance the jumping
velocity based on protruding structures.