The unique self-cleaning
feature of lotus-like superhydrophobic
(SH) surface attracted world-wide interests in recent years. However, the
mechanism of the self-cleaning phenomena remains unclear. Here, we attempt to provide
a comprehensive understanding of why self-cleaning of the particles with a
broad range of size can be realized on the lotus-like SH surfaces. After
measurements and analysis of the force involved at the interface, we conclude
that there are four main preconditions for self-cleaning: 1) CA > 90°; 2) Low enough sliding angle; 3) Low
enough adhesion force; and 4) Proper particle size. However, as far as the
lotus-like SH surface and typical dust are concerned, all the preconditions
will be satisfied automatically. We also observe that, the particles with a
broad range of size (from submicron level to the millimeter level) and density
(virtually no limit) can be driven by water droplet on the lotus-like SH
surface. This interesting finding may be helpful for the design of novel
engineering system at the micron-millimeter scale in the future.
