This new ultrahard material inspired by nature could make uncuttable bike locks

By Adele Peters

Bike locks don’t work well: More than two million bikes are stolen each year in North America alone. Even when a lock might slow down a thief, it’s fairly easy to finish the job in a crowded city, even with lots of people paying attention, as these old viral videos repeatedly demonstrated. But a new material—the first artificial material that can’t be cut—may change that.

“The inspiration came from nature, from biological structures,” says Stefan Szyniszewski, an engineering professor at the U.K.’s Durham University who worked with a team of researchers to develop the uncuttable material, made from ceramic spheres embedded in a cellular structure made of metallic foam. The researchers started by looking at the structure of abalone shells, which are made from a relatively weak material but arranged in a way that means sharks can’t easily bite through the shell. “The shell is 2,000 times harder to crack than the bricks that it’s made of,” says Szyniszewski.

Of course, a power tool like an angle grinder works differently than the jaws of a shark, so the researchers kept working on the design of the material. “I realized that there is this vulnerability of the cutting tools to vibrations,” he says. “When things move very fast, they have a lot of energy. And if we can somehow amplify this variable it should disrupt the cutting.” The ceramic spheres inside the material vibrate so much that it blunts the tool attempting to cut through. As some of the spheres also break apart into small, hard fragments, those pieces act like rough sandpaper, further wearing down the tool. In experiments described in a new paper in Scientific Reports, the material, called Proteus, couldn’t be cut by an angle grinder, drill, or water jet.

The cellular structure is also partly inspired by the peel of a grapefruit, which is strong but lightweight. “We wanted the material to be light, because most protective structures are quite heavy,” Szyniszewski says. “When you think of security doors or armored steel, it’s very heavy. And if you look at protective structures in nature, like the peel of a grapefruit, they’re usually very light.”

The resulting material could be used for a variety of applications, from protective equipment for people working with dangerous machinery to the doors of a vault in a bank. But it’s possible that bike locks could be one of the first products to come to market; Szyniszewski says that he’s already been contacted by a bike lock manufacturer that wants to use the material.

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