In the field of metamaterials—engineered materials with tailored microstructures—the dominant pursuit has long been “stronger is better.” These synthetic materials often mimic lattice structures to maximize stiffness and strength, but this traditionally comes at the expense of flexibility. Now, MIT engineers have broken new ground by developing a metamaterial that is both strong and stretchable, challenging a long-standing trade-off in materials science.

The innovation, detailed in Nature Materials, centers on a “double-network” design inspired by hydrogels. Hydrogels achieve their stretchiness and toughness by combining two polymer networks—one stiff, the other soft. Adapting this idea to metamaterials, the MIT team engineered a structure consisting of rigid struts interwoven with softer, spring-like coils, both printed from a plexiglass-like polymer using ultra-precise two-photon lithography.

The resulting material exhibited remarkable mechanical properties, stretching up to three times its original length—a tenfold improvement over conventional rigid lattice metamaterials made from the same polymer. It also withstood significantly more stress without catastrophic failure.

The material’s resilience arises from the interplay between its rigid and soft components. When stressed, the brittle struts begin to crack but do not cause immediate failure. Instead, the surrounding coiled network becomes entangled with the fractured pieces, absorbing and dissipating energy much like tangled spaghetti. This prevents cracks from propagating directly through the structure and allows it to deform more before breaking.

Surprisingly, the researchers found that introducing defects—tiny, intentional holes in the design—further improved performance, doubling the stretch and tripling the energy absorbed before failure. The defects enhanced stress distribution and increased the entanglement between fibers, contributing to both toughness and flexibility.

Lead researcher Carlos Portela and his team envision the approach being used to create tear-resistant textiles, flexible electronics, robust chip packaging, and biocompatible scaffolds for tissue repair. Since the double-network architecture can be adapted to other materials, including ceramics, metals, and glass, the technique opens up new avenues for designing multifunctional materials—ones that are not just mechanically robust, but also responsive to temperature, conductive, or self-healing.

“We’re opening up a new design space for metamaterials,” says Portela. “Now we can imagine materials that are strong, flexible, and multifunctional—traits that were once thought to be mutually exclusive.”

By Impact Lab