Dynamics of leaves with different wettability due to raindrop impact

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PI: Jung, SunghwanProposal Number: 1604424Based on how easy it is for a surface to be wetted by water, it can be hydrophilic or hydrophobic. The proposed research is inspired by biological surfaces, like leaves, that exhibit different wetting behavior in their lifetime, and turn from hydrophobic to hydrophilic as natural or man-made pollutants interact with their surface. Investigating how the dynamics of drops splashing on leaves change because of changes on surface characteristics is important for understanding early catastrophic leaf loss and developing methods to avoid it. This can have further implications on predicting levels of food and forest resources.Most of the previous work done by biologists and biochemists about shedding of leafs, has focused on acute chemical effects of air contaminants on leaf surfaces. Nevertheless, both the physical mechanism of a leaf turning hydrophilic and the dynamical aspects of hydrophilic leaves in response to raindrops are not well understood, which may significantly contribute to catastrophic leaf loss after rain. The PI proposes to investigate the interplay between a leaf?s wettability, elasticity, and drop spreading, inspired by a raindrop impacting a leaf in nature. First, the mechanism of transitioning from hydrophobic to hydrophilic leaves will be explored. Secondly, the spreading dynamics of a droplet on a curved substrate will be formulated both macroscopically and microscopically in terms of wettability and a falling speed, which will allow the estimation of an impact force and drop-spreading radius on the leaf. Finally, a leaf?s mechanical moduli and ultimate strengths will be characterized, in order to understand bending and torsional deformations of a leaf upon drop impact. The PI will pursue personal and educational interests for students with disabilities. As an educational objective, the PI will develop research programs that assist disabled students in overcoming the difficulties encountered in the current educational system, due to impaired social and communication skills. A proposed peer-buddy program is designed for students with autism or other social impairments by exposing them to laboratory research along with typical peers in structured environments. An inclusive environment would provide the students with structured research opportunities, which would help to develop the confidence and capacity needed to effectively communicate and collaborate with their peers, and eventually become future engineers or scientists.