Madden Ian P, Wang Linlin, Simmchen Juliane, Luijten Erik
Department of Materials Science and Engineering, Northwestern University, Evanston, IL, 60208, USA.
Department of Physical Chemistry, TU Dresden, Zellescher Weg 19, 01062, Dresden, Germany.
Small. 2022 May;18(21):e2107023. doi: 10.1002/smll.202107023. Epub 2022 Mar 19.
Active particles are known to exhibit collective behavior and induce structure in a variety of soft-matter systems. However, many naturally occurring complex fluids are mixtures of active and passive components. The authors examine how activity induces organization in such multi-component systems. Mixtures of passive colloids and colloidal micromotors are investigated and it is observed that even a small fraction of active particles induces reorganization of the passive components in an intriguing series of phenomena. Experimental observations are combined with large-scale simulations that explicitly resolve the near- and far-field effects of the hydrodynamic flow and simultaneously accurately treat the fluid-colloid interfaces. It is demonstrated that neither conventional molecular dynamics simulations nor the reduction of hydrodynamic effects to phoretic attractions can explain the observed phenomena, which originate from the flow field that is generated by the active colloids and subsequently modified by the aggregating passive units. These findings not only offer insight into the organization of biological or synthetic active-passive mixtures, but also open avenues to controlling the behavior of passive building blocks by means of small amounts of active particles.
已知活性粒子会表现出集体行为，并在各种软物质系统中诱导形成结构。然而，许多天然存在的复杂流体是活性和被动成分的混合物。作者研究了活性如何在这种多组分系统中诱导组织形成。研究了被动胶体和胶体微马达的混合物，观察到即使是一小部分活性粒子也会在一系列有趣的现象中诱导被动成分的重新组织。实验观察结果与大规模模拟相结合，该模拟明确解析了流体动力流的近场和远场效应，并同时精确处理流体 - 胶体界面。结果表明，传统的分子动力学模拟以及将流体动力效应简化为电泳吸引力都无法解释所观察到的现象，这些现象源于由活性胶体产生并随后由聚集的被动单元修改的流场。这些发现不仅为生物或合成活性 - 被动混合物的组织提供了见解，还开辟了通过少量活性粒子控制被动构建块行为的途径。
