Institute of Applied Physics, Karlsruhe Institute of Technology, 76128 Karlsruhe, Germany.
Institute of Nanotechnology, Karlsruhe Institute of Technology, 76021 Karlsruhe, Germany.
Science. 2017 Nov 24;358(6366):1072-1074. doi: 10.1126/science.aao4640.
Rationally designed artificial materials enable mechanical properties that are inaccessible with ordinary materials. Pushing on an ordinary linearly elastic bar can cause it to be deformed in many ways. However, a twist, the counterpart of optical activity in the static case, is strictly zero. The unavailability of this degree of freedom hinders applications in terms of mode conversion and the realization of advanced mechanical designs using coordinate transformations. Here, we aim at realizing microstructured three-dimensional elastic chiral mechanical metamaterials that overcome this limitation. On overall millimeter-sized samples, we measure twists per axial strain exceeding 2°/%. Scaling up the number of unit cells for fixed sample dimensions, the twist is robust due to metamaterial stiffening, indicating a characteristic length scale and bringing the aforementioned applications into reach.
合理设计的人工材料能够实现普通材料无法达到的机械性能。推动普通的线性弹性棒可以使其以多种方式变形。然而，扭转，即静态光学活性的对应物，严格为零。这种自由度的缺乏阻碍了模式转换的应用和使用坐标变换实现先进的机械设计。在这里，我们旨在实现克服这一限制的微结构三维弹性手性机械超材料。在整体毫米级的样品上，我们测量的扭转应变超过 2°/％。在固定样品尺寸的情况下增加单元数量，扭转由于超材料变硬而变得稳健，表明存在特征长度尺度，并使上述应用得以实现。
