As anyone who has ever tried sheltering under a pine tree will know, pine needles are brilliant at deflecting raindrops. Even in the heaviest deluge pine trees make wonderful umbrellas. New analysis of pine needles has revealed some of their water-repelling secrets, with potential to revolutionise waterproof fabric design.
Pores become blocked when water pools, preventing a tree from photosynthesising effectively, so shedding water is important for trees in rainy places. Pine forests grow in some of the wettest locations in the world and have honed their water repellency to perfection over millennia.
Using high-speed video Amy Lebanoff and Andrew Dickerson, from the University of Central Florida, filmed what happens to a raindrop when it hits a pine needle with a ridge-shaped profile, versus what happens when it hits a pine needle with a rounded profile. Their findings, published in Physics of Fluids, show that the ridge shaped profile was far more effective at splitting and dispersing raindrops.
Currently most waterproof fabrics are made from fibres with a circular cross-section, but if manufacturers decide to take a needle out of the pine-tree’s book we may start to benefit from fibres with more of a ridge-like profile, designed to blast raindrops apart and shed water fast. As ever, nature has the best designs.
