Droplet Impacting a Cantilever: A Leaf-Raindrop System

Deciduous trees shed their leaves each autumn to survive cold weather. A first step in this process causes the leaves to lose their hydrophobic layer--a phenomenon that is hastened by pollution. Little is known about the physical details of raindrop-leaf interaction as hydrophobicity is changed, yet these details affect premature leaf loss and vulnerability to rainstorms. The authors model the dynamic response of a leaf to a raindrop as that of an elastic cantilever beam, and find that a hydrophobic surface can protect against raindrop impact better than a hydrophilic one. These results could also be used to optimize biomimetic piezoelectric devices for harvesting energy from falling rain.