Metamaterials have been engineered to manipulate their properties.

“A distinctive feature of metamaterials is that their properties depend not on the chemical composition of the framework, but on the structure that is organized in a specific way. As a result, the reaction of a metamaterial to external influences will also be unique,” says the study's author, project leader and associate professor of the Department of Mechanics of Deformable Solid Bodies of the Physical-Technical Faculty of TGU, Linar Akhmetshin.

“In this experiment, I investigated materials with a tetra-chiral structure. Chirality is the property of an object not to coincide with its mirror image. A chiral structure gives the material unusual properties. For instance, if compressed along the Y-axis, it will somehow compress and twist in the X-Z plane. Ordinary materials do not behave this way.”

Another even more intriguing property of metamaterials is their ability to bend and slow down light. A negative refractive index allows objects to be hidden within one of the electromagnetic wave ranges. Therefore, in the future, we may see aircraft that are invisible to radar.

To control the properties of metamaterials, one must understand what happens when their structure changes. The process of discovering new materials can now also rely on computational approaches that enable rapid calculations of the mechanical properties of potential materials. The design of metamaterial structures is ideally suited for digital methods that allow for quick and effective exploration of numerous geometric and structural solutions and their numerical verification.

A researcher from the Physical-Technical Faculty of TGU influenced the samples of metamaterials through compression. The regular elementary cell of the metamaterial did not change its physical and mechanical properties when loaded along three orthotropic axes. Various transformations of the cell (introducing topological defects) led to changes in properties, either enhancing or diminishing the effect.

“Defects are typically perceived negatively, but in my research, they are merely a tool. They enabled the acquisition of a series of new fundamental insights about metamaterials during the final phase of my study—during the compression and failure of samples printed on a 3D printer,” explains Linar Akhmetshin. “Thus, the rotation angle for the regular cell is 1.8°. The introduced topological defect reduced the rotation angle of the cell by more than 60% and significantly increased the material's stiffness. At the same time, the stiffness of the cell with the topological defect varies along the loading axis and increases when the defect is located on the lower side of the cubic sample.”

There are numerous applications for the new knowledge about metamaterials. For example, by programming materials, it is possible to weaken or absorb vibrational energy—thus creating impact-resistant structures with exceptional strength. Utilizing properties like negative refraction allows for new solutions in biomedicine, electronics, and other fields.

Effective use of metamaterials could elevate humanity to a new technological level. The research conducted by the TGU scientist provides new fundamental knowledge necessary to program metamaterials with new functionalities.

The research was carried out as part of the strategic project “Safety Technologies”, supported by the federal program “Priority 2030.” The results of the study are presented in the journal “Bulletin of TGU” (Mechanics).