Scientists have developed a novel material that combines the hardness of steel with the flexibility of rubber, capable of stretching up to four times its original length without tearing. This groundbreaking "rigid yet flexible" material has potential applications in creating high-resilience coatings, dense semiconductor substrates, and durable electronic packaging materials. It can also be used to manufacture scaffolds for cultivating tissues and organs for tissue engineering and repair. Carlos Portela, an associate professor at the University of Minnesota, says, “We are pioneering a new field in mechanical metamaterials.” He explains, “You can stamp this dual-network metal or ceramic, achieving multiple advantages because it requires less energy to break, and its tensile properties are excellent.” This research, co-authored by James Utama Surjadi, Bastien Aymon, and Molly Carton, was recently published in the journal Nature Materials. Inspired by traditional methods using crystalline structures like those in metals and ceramics, Portela and his team sought to enhance the toughness and elasticity of these materials. Several years ago, Portela had a revolutionary idea: instead of simply making the material harder and more rigid, could they design a pattern that would make it denser, more elastic, and yet equally strong? “We realized that the field of metamaterials had not fully explored the influence of soft matter,” he notes. “Until now, most researchers have focused on finding the hardest and most rigid materials possible.” The team began exploring how to create a design that could result in a material that was both harder and more elastic. Unlike traditional methods involving micro-scale pillars, they created a structure from interwoven crystalline columns made of similar materials, often referred to as elastomers. These columns were found to be just as rigid as traditional hard materials but had the added benefits of being much softer and more resilient. Portela reflects, “The material was surprisingly tenacious, but significantly more flexible and adaptive.” In their new research, the team combined two microscopic lattices: one composed of rigid pillars and crossbeams, and another made of softer, woven filaments. Both networks were constructed from the same material, typically alumina, and were printed using a high-precision technique called dual-photon photolithography. When tested, the samples ranged in size from a few millimeters to a few micrometers. The team subjected the material to a series of pressure tests, using specialized clamping machines to measure the force required to stretch it. They also recorded high-resolution images during the stretching and compressing processes to observe the material’s specific behaviors at the microscale. The researchers discovered that the new dual-network design allowed the material to stretch up to three times its length, compared to traditional crystal lattice designs which only stretched up to 10 times under similar conditions. Portela noted that the new material’s tensile strength is derived from the interaction between the rigid pillars and a more complex, mesh-like structure beneath the surface. “You can think of this woven network as a series of beneficial cracks,” Portela explained. “When the entire lattice structure starts to fracture, the damage is localized to the surrounding areas, and these 'beneficial cracks' interact with the lattice flaws, promoting more robust and distributed interactions. This means increased abrasion and energy dissipation.” The team also developed a computational framework to predict the material’s performance based on the design of the stiffness and elasticity networks. They believe this design approach will assist engineers in developing more advanced anti-impact products and composite materials. Surjadi adds, “While this might seem to alter the material's properties, we found that once we introduced these gaps or 'defects,' the material’s stretchability increased by one fold, and its energy dissipation capacity increased by three folds. This gave us a material that is both strong and tough, which are typically contradictory properties.” Looking ahead, Portela says, “We plan to experiment with this method on even softer materials, potentially adding more functionalities such as conductivity or temperature responsiveness. By using different combinations of materials to create the two networks, we can achieve varying responses to temperature changes—becoming more porous in heat and more rigid in cold.” The original source of this information can be found at: https://news.mit.edu/2025/mit-engineers-print-synthetic-metamaterials-strong-and-stretchy-0423