Auxetic materials are being of more and more interest to materials scientists and designers because of their ability to shrink when compressed and expand orthogonally to strain. These materials have a negative Poisson’s ration, meaning that they become thicker perpendicular to the applied force upon being stretched.
The special properties that characterize auxetic materials mean that auxetics can be used to design products with totally new functionalities as well as products with adaptable functions. Some of these products could include medical technology and protective equipment such as bicycle helmets or safety jackets.
Along that line, new research published in Nano Letters and led by Professor Thomas Heine, who teaches Theoretical Chemistry at TU Dresden, showcases a newly discovered phenomenon observed in borophene, which is an atomically thin configuration of boron. Heine used computer modeling to show that when palladium is introduced to borophene, the resulting material, PdB4, expands not only under strain (as an auxetic would) but also under compression (like a normal material would). This behavior, termed, half-auxeticity, is quite rare.
Professor Heine comments: “In addition to thorough characterization in terms of stability, mechanical and electronic properties of the material, we have identified the origin of this half-auxetic character and believe that this mechanism can be used as a design concept for new half-auxetic materials.” Heine’s excitement is hard to hide: “These novel materials could lead to innovative applications in nanotechnology, for example in sensing or magneto-optics. A transfer to macroscopic materials is equally conceivable."