Lippera Kevin, Benzaquen Michael, Michelin Sébastien
LadHyX - Département de Mécanique, CNRS - Ecole Polytechnique, Institut Polytechnique de Paris, 91128 Palaiseau, France.
Soft Matter. 2021 Jan 22;17(2):365-375. doi: 10.1039/d0sm01285h.
Active droplets emit a chemical solute at their surface that modifies their local interfacial tension. They exploit the nonlinear coupling of the convective transport of solute to the resulting Marangoni flows in order to self-propel. Such swimming droplets are by nature anti-chemotactic and are repelled by their own chemical wake or their neighbours. The rebound dynamics resulting from pairwise droplet interactions was recently analysed in detail for purely head-on collisions using a specific bispherical approach. Here, we extend this analysis and propose a reduced model of a generic collision to characterise the alignment and scattering properties of oblique droplet collisions and their potential impact on collective droplet dynamics. A systematic alignment of the droplets' trajectories is observed for symmetric collisions, when the droplets interact directly, and arises from the finite-time rearrangement of the droplets' chemical wake during the collision. For more generic collisions, complex and diverse dynamical regimes are observed, whether the droplets interact directly or through their chemical wake, resulting in a significant scattering.
活性液滴在其表面释放一种化学溶质，这种溶质会改变其局部界面张力。它们利用溶质对流输运与由此产生的马兰戈尼流之间的非线性耦合来实现自我推进。这种游动液滴本质上是抗趋化性的，会被自身的化学尾迹或其相邻液滴排斥。最近，使用一种特定的双球方法，对纯正面碰撞中两两液滴相互作用产生的反弹动力学进行了详细分析。在此，我们扩展了这一分析，并提出了一个通用碰撞的简化模型，以表征倾斜液滴碰撞的排列和散射特性及其对集体液滴动力学的潜在影响。当液滴直接相互作用时，在对称碰撞中观察到液滴轨迹的系统排列，这是由于碰撞过程中液滴化学尾迹的有限时间重排引起的。对于更一般的碰撞，无论液滴是直接相互作用还是通过其化学尾迹相互作用，都会观察到复杂多样的动力学状态，从而导致显著的散射。
