Department of Physics, Brandeis University, Waltham, MA 02453, USA.
Department of Physics, University of California, Santa Barbara, CA 93111, USA.
Science. 2020 Mar 6;367(6482):1120-1124. doi: 10.1126/science.aaz4547.
Topological structures are effective descriptors of the nonequilibrium dynamics of diverse many-body systems. For example, motile, point-like topological defects capture the salient features of two-dimensional active liquid crystals composed of energy-consuming anisotropic units. We dispersed force-generating microtubule bundles in a passive colloidal liquid crystal to form a three-dimensional active nematic. Light-sheet microscopy revealed the temporal evolution of the millimeter-scale structure of these active nematics with single-bundle resolution. The primary topological excitations are extended, charge-neutral disclination loops that undergo complex dynamics and recombination events. Our work suggests a framework for analyzing the nonequilibrium dynamics of bulk anisotropic systems as diverse as driven complex fluids, active metamaterials, biological tissues, and collections of robots or organisms.
拓扑结构是描述多种多体系统非平衡动力学的有效描述符。例如，运动的点状拓扑缺陷捕捉了由耗能各向异性单元组成的二维活性液晶的显著特征。我们将产生力的微管束分散在无源胶体液晶中，形成三维活性向列相。光片显微镜以单束分辨率揭示了这些活性向列相毫米级结构的时间演化。主要的拓扑激发是扩展的、电荷中性的位错环，它们经历复杂的动力学和复合事件。我们的工作为分析各种各向异性体系的非平衡动力学提供了一个框架，这些体系包括驱动复杂流体、活性超材料、生物组织以及机器人或生物体的集合。
