Product development in its many fashions always takes a lot of time. One breakthrough can lead to a chain reaction of others. In this case, the inspiration of biomimcry doubles moves long-lived, self-cleaning surfaces closer to a reality.
THE repulsive powers of lotus leaves are the stuff of legend. Water sprayed onto them forms instantly into silvery beads (see picture) and rolls right off again—carrying any dirt on the leaf’s surface with it.
The physics behind this impressive and beautiful phenomenon is well understood. Lotus leaves repel water because they are covered with minuscule waxy nodules that stop water molecules bonding with a leaf’s surface tissues, meaning those molecules bond with each other instead. That arrangement has been replicated in several man-made materials. Unfortunately, these are easily damaged by abrasion—and, not being alive, cannot regrow and repair themselves. They are thus hard to commercialise, which is a pity, because the self-cleaning, self-drying surfaces they create could be of great value. A technique just described in Langmuir by Jürgen Rühe of the University of Freiburg, in Germany, may, however, fix this problem by giving lotus-like materials the ability to regenerate when damaged.
Dr Rühe’s approach is to mimic a second living organism—this time an animal, the lizard. As lizards grow, their scales do not grow with them. Instead, old scales are shed and replaced from below by new ones. Dr Rühe theorised that it might likewise be possible to create a stack of lotus-like layers that would flake off when damaged, revealing a pristine surface beneath.
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