Yang Xiang, Ren Chenyang, Cheng Kangjun, Zhang H P
School of Physics and Astronomy and Institute of Natural Sciences, Shanghai Jiao Tong University, Shanghai 200240, China.
School of Physical Science and Technology, Soochow University, Suzhou 215006, China.
Phys Rev E. 2020 Feb;101(2-1):022603. doi: 10.1103/PhysRevE.101.022603.
We perform experiments on an active chiral fluid system of self-spinning rotors in a confining boundary. Along the boundary, actively rotating rotors collectively drive a unidirectional material flow. We systematically vary rotor density and boundary shape; boundary flow robustly emerges under all conditions. Flow strength initially increases then decreases with rotor density (quantified by area fraction ϕ); peak strength appears around a density ϕ=0.65. Boundary curvature plays an important role: flow near a concave boundary is stronger than that near a flat or convex boundary in the same confinements. Our experimental results in all cases can be reproduced by a continuum theory with single free fitting parameter, which describes the frictional property of the boundary. Our results support the idea that boundary flow in active chiral fluid is topologically protected; such robust flow can be used to develop materials with novel functions.
我们在一个受限边界内的自旋转转子的活性手性流体系统上进行实验。沿着边界，主动旋转的转子共同驱动单向物质流。我们系统地改变转子密度和边界形状；在所有条件下边界流都能稳健地出现。流动强度最初随转子密度（由面积分数ϕ量化）增加然后减小；峰值强度出现在密度ϕ = 0.65左右。边界曲率起着重要作用：在相同限制条件下，凹边界附近的流动比平边界或凸边界附近的流动更强。我们所有情况下的实验结果都可以由一个具有单个自由拟合参数的连续介质理论再现，该理论描述了边界的摩擦特性。我们的结果支持这样一种观点，即活性手性流体中的边界流受到拓扑保护；这种稳健的流动可用于开发具有新功能的材料。
