We focus on the self-propelled motion of an oil/aqueous droplet within an aqueous/oil phase, which originates from an interfacial chemical reaction of surfactant. Droplet motion has been explained by mathematical models; however, these models require the assumption that the chemical reaction increases the interfacial tension. On the other hand, several experimental reports have demonstrated self-propelled motion with the chemical reaction decreasing the interfacial tension. We aimed to construct an improved mathematical model that explains these experimental observations. We considered the concentrations of the reactant and product on the interface and of the reactant in the bulk. Our numerical calculations indicate that the droplet potentially moves regardless of the increase or decrease in interfacial tension. In addition, the reaction rate and size dependencies of the droplet speed observed in experiments were well reproduced by our model. These results indicate that our model is universally applicable for droplet motion.

中文翻译：

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产品对表面活性剂化学反应驱动的自发液滴运动的影响

我们专注于油/水液滴在水/油相中的自推进运动，这是由于表面活性剂的界面化学反应引起的。液滴运动已通过数学模型进行了解释；但是，这些模型需要假设化学反应会增加界面张力。另一方面，一些实验报告证明了自推进运动，其中化学反应降低了界面张力。我们旨在构建一个可以解释这些实验观察结果的改进的数学模型。我们考虑了界面上反应物和产物的浓度以及本体中反应物的浓度。我们的数值计算表明，无论界面张力的增大或减小，液滴都可能移动。此外，我们的模型很好地再现了实验中观察到的反应速度和液滴速度的大小依赖性。这些结果表明我们的模型普遍适用于液滴运动。