EFFECTS OF SURFACE MORPHOLOGY

1
EFFECTS OF SURFACE MORPHOLOGY ON
SUPERHYDROPHOBICITY AND BUOYANCY OF THE CABBAGE
LEAF AND THE VACNTS CARPET
E. Lepore, M.Giorcelli, C. Saggese, N.
Pugno and A. Tagliaferro
Laboratory of Bio-inspired Nanomechanics,
Department of Structural Engineering, Politecnico
di Torino - Applied Science Technology
Department - Polytecnich of Turin -
Chemistry, Material and Chemical Engineering
Department "Giulio Natta" (CMIC), Polytechnich of
Milan mauro.giorcelli_at_polito.it
In this work we have studied two types of
nanostructured surfaces the cabbage leaf and a
vertical aligned carbon nanotubes carpet. These
surfaces are characterized by means of contact
angle, sliding angle, sliding volume and sliding
speed measurements. Results are correlated with
nano-morphology surface and investigated by
scanning electron microscopy. Buoyancy behavior
of different surfaces has been investigated
through dedicated measurements which have allowed
us to determine forces involved on surface. In
this paper the buoyancy behavior of these
surfaces is compared with one of water striders
leg. Finally, we demonstrate that cabbage leaf
and vertical aligned carbon nanotubes carpet have
some common features with the water striders leg.
1. SURFACE CHARACTERIZATION
2. MEASUREMENTS OF WETTABILITY
SVSliding Volume SSSliding Speed CA Contact
Angle SASliding Angle
3. MEASUREMENTS OF FLOATING
Theoretically, 1 m2 of the L side of the cabbage
leaf (or VACNTs carpet) could be able to support
on average ? 3 kg. This result underline the
higher bearing capacity of the natural surface
(in particular, the L side of cabbage leaf), if
compared to the artificial one (VACNTs carpet).
Upper (adaxial) and lower (abaxial) sides of the
natural cabbage leaf of Brassica oleracea.
Surface Weight (mg) Times weight
Leaf 89 2
VACNTs 200 5
Insects leg - 15
4.CONCLUSIONS
VACNTs mechanical strength - low density.
The hierarchical arrangement of structures of the
surface has a strong impact on the macroscopic
observable surface effects. The presence of the
surface roughness on multiple scales is necessary
to increase the wetting resistance and to induce
a self-cleaning behavior and the water floating
capacity, as water striders legs show. We have
demonstrated that the cabbage leaf and the VACNTs
carpet have some common features with the water
striders legs. The carrying load on water is
direct correlated to the superhydrophobic
property and the surface structures, which range
from the nanoscale to the micrometer scale, in
water permit the presence of a thin layer of air
at the immersed surface responsible of this
behavior.
Water striders leg (Gerris Remigis).