Recent experiments have shown that the complex spatio-temporal vortex structures emerging in active fluids are susceptible to weak geometrical constraints. This observation poses the fundamental question of how boundary effects stabilize a highly ordered pattern from seemingly turbulent motion. Here we show, by a combination of continuum theory and experiments on a bacterial suspension, how artificial obstacles guide the flow profile and reorganize topological defects, which enables the design of bacterial vortex lattices with tunable properties. To this end, the continuum model is extended by appropriate boundary conditions. Beyond the stabilization of square and hexagonal lattices, we also provide a striking example of a chiral, antiferromagnetic lattice exhibiting a net rotational flow, which is induced by arranging the obstacles in a Kagome-like array.

最近的实验表明，在活性流体中出现的复杂的时空涡旋结构易受弱几何约束的影响。这一观察提出了一个基本问题，即边界效应如何使看似湍流的运动稳定一个高度有序的图案。在这里，我们通过对细菌悬浮液的连续性理论和实验相结合，展示了人工障碍物如何引导流动剖面并重新组织拓扑缺陷，从而使细菌涡旋晶格的设计具有可调性。为此，通过适当的边界条件扩展了连续体模型。除了稳定正方形和六边形晶格外，我们还提供了一个手征性反铁磁晶格表现出净旋转流的惊人示例，