Abstract

For monolayers of chemically active particles at a fluid interface, collective dynamics is predicted to arise owing to activity-induced Marangoni flow even if the particles are not self-propelled. Here, we test this prediction by employing a monolayer of spherically symmetric active \(\hbox {TiO}_2\) particles located at an oil–water interface with or without addition of a nonionic surfactant. Due to the spherical symmetry, an individual particle does not self-propel. However, the gradients produced by the photochemical fuel degradation give rise to long-ranged Marangoni flows. For the case in which surfactant is added to the system, we indeed observe the emergence of collective motion, with dynamics dependent on the particle coverage of the monolayer. The experimental observations are discussed within the framework of a simple theoretical mean-field model.

Graphic abstract

中文翻译：

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活跃的球体引发了推动集体动力的马兰戈尼流动

摘要

对于流体界面处的单层化学活性粒子，即使粒子不是自推进的，由于活动诱导的 Marangoni 流动，预计会出现集体动力学。在这里，我们通过使用单层球对称活性\(\hbox {TiO}_2\)来测试这个预测。添加或不添加非离子表面活性剂时，位于油水界面的颗粒。由于球对称性，单个粒子不会自行推进。然而，光化学燃料降解产生的梯度会产生长程马兰戈尼流。对于将表面活性剂添加到系统中的情况，我们确实观察到集体运动的出现，其动力学取决于单层的粒子覆盖率。实验观察是在一个简单的理论平均场模型的框架内讨论的。

图形摘要