Driven dynamics in dense suspensions of microrollers
Driven dynamics in dense suspensions of microrollers
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DOI：
10.1039/d0sm00879f
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发表时间：
2020-09-14
期刊：
影响因子：
3.4
通讯作者：
Donev, Aleksandar
中科院分区：
文献类型：
--
作者：
Sprinkle, Brennan;van der Wee, Ernest B.;Donev, Aleksandar
我们进行详细的计算和实验测量的驱动动力学的一个密集的，均匀的悬浮液的沉积microrollers驱动的磁场旋转轴平行于地板。我们开发了一个润滑校正的布朗动力学方法驱动的胶体沉积在底壁上方的稠密悬浮液。数值方法增加了附近的颗粒对之间的润滑摩擦，以及颗粒和底壁，远场流体动力相互作用的最小分辨率模型。我们的实验结合联合收割机荧光标记与粒子跟踪的轨迹的单个粒子在一个稠密的悬浮液，并测量其推进速度。以前的计算研究[B. Sprinkleet等人，化学物理学杂志，2017，147，244103]预测，在足够高的密度下，微辊的均匀悬浮液分离成两层，在壁的正上方的慢单层和在底层顶部的快层。在这里，我们验证了这一预测，表现出良好的定量协议的双峰分布的颗粒速度预测的润滑校正的布朗动力学和那些在实验中测量。计算方法准确地预测了实验中观察到的粒子在慢层和快层之间切换的速率。我们还使用我们的数值方法来证明成对润滑在胶体微辊致密单层中运动诱导相分离中的重要作用，正如最近提出的Quincke辊悬浮液[D. Geyeret al.，Phys. Rev. X，2019，9（3），031043]。
We perform detailed computational and experimental measurements of the driven dynamics of a dense, uniform suspension of sedimented microrollers driven by a magnetic field rotating around an axis parallel to the floor. We develop a lubrication-corrected Brownian dynamics method for dense suspensions of driven colloids sedimented above a bottom wall. The numerical method adds lubrication friction between nearby pairs of particles, as well as particles and the bottom wall, to a minimally-resolved model of the far-field hydrodynamic interactions. Our experiments combine fluorescent labeling with particle tracking to trace the trajectories of individual particles in a dense suspension, and to measure their propulsion velocities. Previous computational studies [B. Sprinkleet al.,J. Chem. Phys., 2017,147, 244103] predicted that at sufficiently high densities a uniform suspension of microrollers separates into two layers, a slow monolayer right above the wall, and a fast layer on top of the bottom layer. Here we verify this prediction, showing good quantitative agreement between the bimodal distribution of particle velocities predicted by the lubrication-corrected Brownian dynamics and those measured in the experiments. The computational method accurately predicts the rate at which particles are observed to switch between the slow and fast layers in the experiments. We also use our numerical method to demonstrate the important role that pairwise lubrication plays in motility-induced phase separation in dense monolayers of colloidal microrollers, as recently suggested for suspensions of Quincke rollers [D. Geyeret al.,Phys. Rev. X, 2019,9(3), 031043].