Condensed Matter Department, J Stefan Institute, Jamova 39, Ljubljana 1000, Slovenia.
Nat Commun. 2013;4:1489. doi: 10.1038/ncomms2486.
Topology has long been considered as an abstract mathematical discipline with little connection to material science. Here we demonstrate that control over spatial and temporal positioning of topological defects allows for the design and assembly of three-dimensional nematic colloidal crystals, giving some unexpected material properties, such as giant electrostriction and collective electro-rotation. Using laser tweezers, we have assembled three-dimensional colloidal crystals made up of 4 μm microspheres in a bulk nematic liquid crystal, implementing a step-by-step protocol, dictated by the orientation of point defects. The three-dimensional colloidal crystals have tetragonal symmetry with antiparallel topological dipoles and exhibit giant electrostriction, shrinking by 25-30% at 0.37 V μm(-1). An external electric field induces a reversible and controllable electro-rotation of the crystal as a whole, with the angle of rotation being ~30° at 0.14 V μm(-1), when using liquid crystal with negative dielectric anisotropy. This demonstrates a new class of electrically highly responsive soft materials.
拓扑学长期以来一直被认为是一门抽象的数学学科，与材料科学几乎没有联系。在这里，我们证明了对拓扑缺陷的空间和时间定位的控制可以设计和组装三维向列胶体晶体，赋予一些意想不到的材料特性，如巨大的电伸缩和集体电旋转。我们使用激光镊子在向列液晶体中组装了由 4μm 微球组成的三维胶体晶体，实施了一个由点缺陷取向决定的分步协议。三维胶体晶体具有四方对称性和反平行拓扑偶极子，并表现出巨大的电伸缩性，在 0.37Vμm(-1)时收缩 25-30%。当使用具有负介电各向异性的液晶时，外电场会引起晶体整体的可逆和可控电旋转，在 0.14Vμm(-1)时旋转角度约为 30°。这证明了一类新的电响应性强的软材料。
