Previous studies have shown that air pollution and wind erosion, which damage a leaf's epicuticular wax layer, can change leaf surface properties from hydrophobic to hydrophilic. However, the dynamic response of a damaged leaf to a raindrop impact has not been investigated and could clarify the direct influence of changes in wettability on early leaf abscission. In this study, we investigate how leaves with different surface properties respond to falling raindrops, viewing this as a unique

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... m of coupled elasticity and drop dynamics. An elastic beam with tunable surface wettability properties is used as a simple leaf model. We find that wettable beams experience much higher torque and bending energy than non-wettable beams. This is because a drop sticks to a wettable beam, while a drop falls off a non-wettable beam. An analytical model using momentum balance and simple cantilever beam theory quantifies the bending energy and torque experienced by wettable and non-wettable beams. The results elucidate the potential damage caused by raindrops impacting a leaf as a function of its surface wettability, and are correlated with environmental factors contributing to premature changes of leaf surface properties. PACS numbers: