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'Bed of nails' surfaces just won’t get wet

Birds do it. Bees do it. Even the leaves on the trees do it. No, not that. They have surfaces capable of shedding water. In recent years, scientists have jumped into the game, creating a wide variety of coatings capable of shedding very different liquids, such as oil and water. But they haven’t yet managed to create a surface that also repels the “wettest” fluids—those with very low surface tension, such as fluorinated solvents. Until now. Researchers report online today in Science that they’ve engineered glass and metal surfaces to repel virtually all fluids. To do so, they etched the surfaces to resemble a bed of nails, with the heads of the nails—each 20 micrometers across—facing up. That limits the surface area that liquids can contact, a strategy that had been used before. But in this case, the researchers also undercut the head of each “nail” to prevent liquid from invading the gaps in between. Because the etched surfaces don’t use a coating, they can withstand high temperatures, a property that could make them valuable in the production of electronic circuits. They might also lead to surgical instruments that repel blood and other fluids.