A team of international researchers has developed a groundbreaking class of mechanical metamaterials capable of storing and releasing elastic energy at unprecedented levels.
By cleverly twisting rods into a helical shape and integrating them into a new metamaterial structure, they’ve overcome traditional design limits, achieving an enthalpy 2 to 160 times higher than existing materials. This breakthrough opens the door to energy-dense components for robotics, shock absorption, and next-generation machines.
Innovative Approaches to Mechanical Energy Storage
Whether it’s springs for absorbing shocks, mechanical buffers for storing energy, or flexible components in robotics and energy-efficient machines, many modern technologies rely on the ability to store mechanical energy. This involves converting kinetic energy, motion or mechanical work, into elastic energy that can be fully released when needed. A key factor in this process is enthalpy, which refers to how much energy can be stored in and recovered from a material.
According to Professor Peter Gumbsch of the Karlsruhe Institute of Technology (KIT), maximizing enthalpy is no easy task. “The difficulty is to combine conflicting properties: high stiffness, high strength, and large recoverable strain.”
Designing High-Performance Metamaterials
Metamaterials are materials designed with structures not found in nature. By arranging carefully engineered building blocks, researchers can create materials with enhanced or unusual properties. Gumbsch, who also leads the Fraunhofer Institute for Mechanics of Materials in Freiburg, and an international team from China and the U.S. have now developed a mechanical metamaterial that stores elastic energy extremely efficiently.
“At first, we detected a mechanism for storing a high amount of energy in a simple round rod without breaking it or deforming it permanently,” says Gumbsch. “By defining a clever arrangement of the rods, we then integrated this mechanism into a metamaterial.”
Twisting Mechanics for Maximum Energy Retention
The researchers compared their discovery to a traditional bending spring, which can only bend so far before it cracks or deforms permanently due to the high stresses on its surfaces. Inside the spring, stress remains low, making it inefficient for energy storage. But by twisting a rod instead of bending it, the surface experiences more uniform stress, and the volume of low-stress interior material is reduced. Pushing this idea further, the researchers used intense torsion to induce a complex helical buckling pattern, maximizing energy storage while maintaining structural integrity.
Record-High Enthalpy in Novel Material Designs
The researchers managed to integrate such torsionally loaded and helically deformed rods into a metamaterial that can be used macroscopically under uniaxial loads. Simulations helped them predict that the metamaterial would have a high stiffness and thus could absorb large forces. In addition, its enthalpy is 2 to 160 times higher than that of other metamaterials. To confirm this, they conducted simple compression experiments on various metamaterials with mirrored chiral structures.
Future Applications for High-Energy Materials
“Our new metamaterials with their high elastic energy storage capacity have the potential to be used in various areas in the future where both efficient energy storage and exceptional mechanical properties are required,” says Gumbsch. Conceivable applications beside spring-based energy storage include shock absorption or damping as well as flexible structures in robotics or in energy-efficient machines. Alternatively, the twists occurring inside the metamaterials might be used for purely elastic joints.
Reference: “Large recoverable elastic energy in chiral metamaterials via twist buckling” by Xin Fang, Dianlong Yu, Jihong Wen, Yifan Dai, Matthew R. Begley, Huajian Gao and Peter Gumbsch, 12 March 2025, Nature.
DOI: 10.1038/s41586-025-08658-z
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1 Comment
The twist was established to be effective in copper wire years ago. That is what made cat 3 turn to cat 5 and cat 6 cables resulting in greater transmission speeds and higher energy flow. You’d think they would’ve already discovered this a long time ago