Unstable fronts and motile structures formed by microrollers
Unstable fronts and motile structures formed by microrollers
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DOI：
10.1038/nphys3970
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发表时间：
2017-04-01
期刊：
影响因子：
19.6
通讯作者：
Chaikin, Paul
中科院分区：
文献类型：
--
作者：
Driscoll, Michelle;Delmotte, Blaise;Chaikin, Paul
在平衡1和驱动系统(2-5)中，物体凝聚成稳定的星团是自然发生的。人们普遍认为，潜在的相互作用(6)、耗尽力(7)或传感(8)是唯一可以创建长寿命紧凑结构的机制。在这里，我们展示了持久的运动结构可以自发地形成单独的流体动力相互作用，没有感知或潜在的相互作用。我们通过实验和大规模的三维模拟，研究了悬浮和平移在地板上方的胶体滚子系统中这种结构的形成。在这个系统中，星团起源于一种以前未被报道的指法不稳定性，即手指从不稳定的锋面到形成突变的“生物”，其大小由粒子在地板上的高度来选择。这些生物是系统的稳定状态，移动速度比单个粒子快得多，并对不断变化的驱动力做出快速反应。利用旋转磁场设定的速度和方向，这些有源结构为微尺度的引导传输、流动产生和混合提供了有趣的可能性。
Condensation of objects into stable clusters occurs naturally in equilibrium1 and driven systems(2-5). It is commonly held that potential interactions(6), depletion forces(7), or sensing(8) are the only mechanisms which can create long-lived compact structures. Here we show that persistent motile structures can formspontaneously fromhydrodynamic interactions alone, with no sensing or potential interactions. We study this structure formation in a system of colloidal rollers suspended and translating above a floor, using both experiments and large-scale three-dimensional simulations. In this system, clusters originate from a previously unreported fingering instability, where fingers pinch offer from an unstable front to formautonomous 'critters', whose size is selected by the height of the particles above the floor. These critters are a stable state of the system, move much faster than individual particles, and quickly respond to a changing drive. With speed and direction set by a rotating magnetic field, these active structures offer interesting possibilities for guided transport, flow generation, and mixing at the microscale.