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Anisotropic dynamics of a self-assembled colloidal chain in an active bath.
Soft Matter ( IF 2.9 ) Pub Date : 2020-06-10 , DOI: 10.1039/d0sm00318b
Mehdi Shafiei Aporvari 1 , Mustafa Utkur 2 , Emine Ulku Saritas 2 , Giovanni Volpe 3 , Joakim Stenhammar 4
Affiliation  

Anisotropic macromolecules exposed to non-equilibrium (active) noise are very common in biological systems, and an accurate understanding of their anisotropic dynamics is therefore crucial. Here, we experimentally investigate the dynamics of isolated chains assembled from magnetic microparticles at a liquid–air interface and moving in an active bath consisting of motile E. coli bacteria. We investigate both the internal chain dynamics and the anisotropic center-of-mass dynamics through particle tracking. We find that both the internal and center-of-mass dynamics are greatly enhanced compared to the passive case, i.e., a system without bacteria, and that the center-of-mass diffusion coefficient D features a non-monotonic dependence as a function of the chain length. Furthermore, our results show that the relationship between the components of D parallel and perpendicular with respect to the direction of the applied magnetic field is preserved in the active bath compared to the passive case, with a higher diffusion in the parallel direction, in contrast to previous findings in the literature. We argue that this qualitative difference is due to subtle differences in the experimental geometry and conditions and the relative roles played by long-range hydrodynamic interactions and short-range collisions.

中文翻译:

活性浴中自组装胶体链的各向异性动力学。

暴露于非平衡(活性)噪声的各向异性大分子在生物系统中非常常见,因此准确了解其各向异性动力学至关重要。在这里,我们通过实验研究了由磁性微粒在液-气界面处组装并在由活动性大肠杆菌组成的主动浴中移动的孤立链的动力学。我们通过粒子跟踪研究了内部链动力学和各向异性质心动力学。我们发现,与被动情况(无细菌的系统)相比,内部和质量中心动力学都得到了极大的增强,并且质量中心扩散系数D具有非单调依赖关系,是链长的函数。此外,我们的结果表明,与无源情况相比,在有源浴中保留了相对于所施加磁场方向平行和垂直的D分量之间的关系,与之相反,在平行方向上的D分量较高。文献中的先前发现。我们认为,这种质的差异是由于实验几何形状和条件的细微差异以及远距离流体动力相互作用和近距离碰撞所起的相对作用。
更新日期:2020-06-24
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