Science News for Students - Spring 2021

one day at a Swiss cafe. They saw a tile pattern on the floor. For some reason, that design made them think of rotation. “After a number of mistakes, we got to the idea of introducing chirality—this twist idea,” he says. That was the real innovation. Researchers used to have only two main ways to create the types of sound-dampening band- gaps that this newmaterial demonstrates, says Marco Miniaci. “You can make the material very dense, or very soft.” Miniaci is an engineer. He works at EMPA, too, where he led the project with Bergamini. Those past approaches to sound dampening had their limitations, he notes. A dense material will be heavy. It also can be poten- tially costly to make, use or maintain. If it’s soft, however, the material may not be rugged enough

to stand up in construction designs. The new material is the best of both alternatives, Miniaci says—lightweight and durable. The EMPA team is nowworking with manu- facturers to find ways to put their structural spin—or twist—on the materials that will be used to build cars, planes and other products of the future. That should be possible, says Sánchez-Dehesa. Moreover, the new material can block a wider range of wavelengths and, potentially, lower pitches. He says that “the design is feasible.” And, he adds, “thanks to advances in 3-D- manufacturing, I see no potential troubles” in building new sound-blocking windows. Their see-through glass would have an invisible, built-in twist. ×

You can’t listen Andrea Bergamini created a model, shown here, to demonstrate how his team’s new innovation could be used to keep conversations private. Their so-called cryptography window consists of two plastic plates, with a series of rotating discs between them. The size of those discs has been chosen to interfere with the frequencies of the human voice. The discs alter sounds passing through the window in such a way that the words are hopelessly muffled. Someone on the outside can view speakers through the window. But what they say will be so distorted that not a single word will be understand- able. And this window works without any need for electronics or power.

EMPA

26 SCIENCE NEWS FOR STUDENTS | Invention & Innovation