Pair interaction of catalytically active colloids: from assembly to escape
Pair interaction of catalytically active colloids: from assembly to escape
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催化活性胶体的配对相互作用：从组装到逃逸
DOI：
10.1017/jfm.2016.317
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发表时间：
2015
影响因子：
3.7
通讯作者：
Ubaldo M. Córdova
中科院分区：
文献类型：
--
作者：
Nima Sharifi;A. Mozaffari;Ubaldo M. Córdova
本文研究了静止流体中两个自推进（主动）胶体在轴对称和非对称两种情况下的动力学和运动轨迹。胶体的自主运动是由于在其表面上不对称地发生的催化化学反应，该反应在颗粒周围产生相互作用的溶质的浓度梯度并驱动颗粒推进。采用解析-数值相结合的方法求解Stokes流型下溶质和胶体间流体力学的耦合质量守恒方程。对于轴对称运动，粒子在近场中的平移游动速度可以增强或减弱（与它们远离时的运动相比），这取决于它们的活动部分的相对取向。此外，可以表明，两个对称颗粒的不同表面活性，例如惰性颗粒与催化颗粒或两个催化颗粒，也可以导致推进，其中惰性颗粒和催化颗粒的远场游泳速度分别衰减为${\sim}1/{\it\Delta}^{2}$和${\sim}1/{\it\Delta}^{5}$，${\it\Delta}$是无因次中心到中心距离。对于非对称运动，我们的分析表明两种可能的情况下对催化活性颗粒的轨迹：要么颗粒的方法，接触和组装或它们相互作用，并远离对方（逃逸）。据发现，粒子旋转的方向是决定逃逸或组装的情况下，由于流体动力学和泳动效应之间的相互作用的关键因素。基于分析，作为反应表面覆盖率和它们相对于彼此的初始相对取向的函数的催化活性颗粒的对轨迹的相图被勾画。我们相信这项研究具有重要的意义，在阐明集体行为的自泳自推进胶体，并肯定会为实验设计和控制主动系统的指导。
The dynamics and pair trajectories of two self-propelled (active) colloids in a quiescent fluid for both axisymmetric and asymmetric cases are reported. The autonomous motions of the colloids are due to a catalytic chemical reaction taking place asymmetrically on their surfaces that generates a concentration gradient of interactive solutes around the particles and actuates particle propulsion. A combined analytical–numerical technique was developed to solve the coupled mass conservation equation for the solute and the hydrodynamics between the colloids in the Stokes flow regime. For axisymmetric motions, the translational swimming velocities of the particles in the near field can be enhanced or weakened (compared to their motions when they are far apart) depending on the relative orientations of their active sections. Moreover, it can be shown that different surface activities of two symmetric particles, e.g. an inert versus a catalytic particle or two catalytic particles, can also lead to a propulsion where the far-field swimming velocity for the inert and the catalytic particle attenuate as ${\sim}1/{\it\Delta}^{2}$ and ${\sim}1/{\it\Delta}^{5}$ respectively, ${\it\Delta}$ is the non-dimensional centre-to-centre distance. For asymmetric motions, our analysis indicates two possible scenarios for pair trajectories of catalytically active particles: either the particles approach, come into contact and assemble or they interact and move away from each other (escape). It is found that the direction of particle rotations is the key factor in determining the escape or assembly scenario due to an interplay between both hydrodynamic and phoretic effects. Based on the analysis, a phase diagram is sketched for the pair trajectory of the catalytically active particles as a function of reacting surface coverages and their initial relative orientations with respect to each other. We believe this study has important implications in elucidation of collective behaviours of autophoretically self-propelled colloids and would be certainly a guide for experimentalists to design and control active systems.
影响因子：
13.3
作者：
Kagan, Daniel;Laocharoensuk, Rawiwan;Wang, Joseph
通讯作者：
Wang, Joseph
影响因子：
8.6
作者：
A. Zöttl;H. Stark
通讯作者：
A. Zöttl;H. Stark
影响因子：
2.4
作者：
Ebbens, Stephen;Tu, Mei-Hsien;Golestanian, Ramin
通讯作者：
Golestanian, Ramin