A D V A N C E D M A T E R I A L S & P R O C E S S E S | J U L Y / A U G U S T 2 0 2 2 9 of Massachusetts, Amherst. One of the most desirable shapes for materials scientists, and with a wide range of applications, double gyroids have historically eluded scientists’ understanding. This unique structure is comprised of a single layer that twists up into a saddle-shaped layer, which then fits into a cubic box in such a way that its surface area stays as small as possible—that’s a gyroid. A double-gyroid forms when a second material, also twisted into a gyroid, fills in the gaps in the first gyroid. Each gyroidal material forms a network of tubes that interpenetrates the other. Together, they form an enormously complex material that is both symmetrical on all sides, like many crystals, yet pervaded by labyrinthine channels, each formed from different molecular units. Because this material is a hybrid of two gyroids, it can be engineered to have contradictory properties. The research team built upon a previous theoretical model, adding a heavy dose of thermodynamics and a new approach to thinking about the packing problem—or how best to fill a finite container with material—borrowed from computational geometry and known as the medial map. The team’s updated theoretical model not only explains the puzzling formation of double-gyroids but holds promise for understanding how the packing problem works in a much broader array of self-assembled superstructures, such as double-diamonds and double-primitives—or even structures that have yet to be discovered. The end goal is to be able to engineer a wide variety of materials that take advantage of the double-gyroid’s structure and that can help advance a wide range of technologies from rechargeable batteries to light-reflecting coatings. umass.edu. In a double-gyroid, two materials (pictured as red and blue) interpenetrate each other. Courtesy of Reddy et al., Nature Communications, 2022.
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