An international research team coordinated at KIT (Karlsruhe Institute of Technology) has developed mechanical metamaterials with a high elastic energy density. Highly twisted rods that deform helically provide these metamaterials with a high stiffness and enable them to absorb and release large amounts of elastic energy. The researchers conducted simple compression experiments to confirm the initial theoretical results. Their findings have been published in the journal Nature.

Storage of mechanical energy is required for many technologies, including springs for absorbing energy, buffers for mechanical energy storage, or flexible structures in robotics or energy-efficient machines. Kinetic energy, i.e., motion energy or the corresponding mechanical work, is converted into elastic energy in such a way that it can be fully released again when required.

The key characteristic here is enthalpy—the energy density that can be stored in and recovered from an element of the material. Peter Gumbsch, Professor for mechanics of materials at KIT’s Institute for Applied Materials (IAM), explains that achieving the highest possible enthalpy is challenging: “The difficulty is to combine conflicting properties: high stiffness, high strength and large recoverable strain.”