Beijing National Laboratory for Condensed Matter Physics and Laboratory of Soft Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China.
School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100049, China.
Phys Rev Lett. 2023 Oct 13;131(15):158301. doi: 10.1103/PhysRevLett.131.158301.
We perform optical-tweezers experiments and mesoscale fluid simulations to study the effective interactions between two parallel plates immersed in bacterial suspensions. The plates are found to experience a long-range attraction, which increases linearly with bacterial density and decreases with plate separation. The higher bacterial density and orientation order between plates observed in the experiments imply that the long-range effective attraction mainly arises from the bacterial flow field, instead of the direct bacterium-plate collisions, which is confirmed by the simulations. Furthermore, the hydrodynamic contribution is inversely proportional to the squared interplate separation in the far field. Our findings highlight the importance of hydrodynamics on the effective forces between passive objects in active baths, providing new possibilities to control activity-directed assembly.
我们通过光镊实验和介观流体模拟来研究浸入细菌悬浮液中的两块平行板之间的有效相互作用。发现两块板之间存在长程吸引力，其随细菌密度线性增加，并随板间距的增大而减小。实验中观察到的较高细菌密度和板间取向有序性表明，长程有效吸引力主要来自细菌流场，而不是细菌与板的直接碰撞，这一结论得到了模拟的证实。此外，在远场中，流体动力贡献与板间距离的平方成反比。我们的研究结果强调了在活性浴中被动物体之间的有效力中流体动力学的重要性，为控制活性导向组装提供了新的可能性。
