Numerous
fascinating hierarchical surfaces from nature, including
cactus spines, rice leaves, Namib desert beetle, spider silks, and
pitcher plants, have been thoroughly investigated to emulate and architect
superior surfaces for capturing sustainable, clean, and safe freshwater
from the atmosphere. Hitherto, the adaxial side of biological surfaces
has been meticulously investigated for wettability and atmospheric
water harvesting (AWH) applications. However, the abaxial face has
not yet attracted much scientific scrutiny. Here, we revealed the
multifunctional Janus surface traits of Trifolium pratense (i.e., red clover) leaf with extrusive atmospheric water fishing
ability on both adaxial and abaxial faces. Water harvesting is performed
by conical outgrowths (microhairs). The individual hair’s intriguing
topography comprises asymmetric shape and surface roughness, which
plays synergetic roles in water deposition and directional transport.
The water collection quantity on the leaf surface is a function of
hair density, which varies significantly on two sides. Noticeably,
instead of gravitational pull, the hairs perform water reaping competence
under the collective impact of surface energy and Laplace pressure
gradients. Consequently, both straight-up and upside-down water harvesting
are presented. Furthermore, the leaf surface exhibits dual water wettability
features. The upper side manifests the water-repelling and water roll-off
phenomenon. In contrast, the lower surface displays a water-retaining/or
pinning effect. Optical microscopy, scanning electronic microscopy,
real-time optical visualization, and contact angle analysis were employed
to characterize the natural and template specimens. The dorsiventral
asymmetry of the Trifolium leaf examined in this
work could be helpful for a plethora of applications, such as scalable
AWH, rainwater collection, self-cleaning, and adhesive fixtures.
