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Spiders can make up to seven different types of silk. The strongest is dragline silk, which is used for building webs1.
Fact: Darwin’s bark spider (Caerostris darwini) can spin silk threads2 that can measure up to 25 m.
Spider dragline silk is made of fibrils comprising proteins that are made of crystalline structures that provide strength and amorphous, formless, regions that provide flexibility.
Infusing metal into spider silk increases its toughness tenfold3. The resulting thread could be used in artificial tendons.
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Shark skin is made up of tooth-like V-shaped scales called dermal denticles that align parallel to the direction of local water flow to reduce drag4.
Fact: The shortfin mako shark (Isurus oxyrinchus) can reach up to 60 miles per hour (100 kilometres per hour) in short bursts5.
A swimsuit made from biomimetic shark skin could increase a human swimmer’s speed by almost 7%, but the likelihood of it being allowed in competitive sport is slim4.
See page S10
The scales of a pine cone are made up of two different layers, each reacting differently to changes in humidity. One layer elongates in damp conditions and the other works to resist this, causing the scales to bend. It is similar to the way a thermostat’s bimetallic strip bends in response to changing temperature6.
Fact: The cones of the knobcone pine (Pinus attenuata) only open their scales to drop seeds in the extreme heat of a wildfire.
Julian Vincent, Univ. Oxford
Researchers have developed smart materials with woollen spikes that are sensitive to relative humidity. The wool spikes open when the wearer sweats and close when the layer dries out.
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The leaves of the lotus plant (Nelumbo spp.) have evolved an intricate structure consisting of papillae covered in a dense coating of wax tubules. Trapped air reduces the liquid-to-surface contact area, so water rolls off the surface and collects dust particles on its way7.
Fact: By 2019, the global nanocoatings market is forecast to reach a value of US$14.2 billion.
Eye of Science/SPL
Synthetic materials with a hierarchical surface, such as those that mimic the lotus leaf, have gaps filled with a lubricant so that the material is stain- as well as water-resistant8.
J. Adam Fenster / Univ. Rochester
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Geckos (Hemidactylus spp.) can climb glass walls and hang from ceilings without a visible method of sticking to them. Researchers found that geckos can adhere to gravity-defying surfaces because of the electrostatic interaction between the molecules in their feet and the molecules on a surface9.
Boston Globe/Getty Images
Fact: Geckos’ feet are so sticky that, in theory, they could support the weight of a 130 kg person hanging from the ceiling10.
Hand pads, each covered in tiles with tiny silicon rubber hairs that mimic geckos’ feet, mean humans can scale walls like lizards. The more force applied to the pads, the stickier they become11.
Eric Eason, Stanford Univ.
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