Table_1_Ionic Tuning of Droplet Motion on Water Surface.DOCX

Herein, the oscillation of an oil droplet on the surface of water is studied. The droplet contains an anionic surfactant that can react with the cations present in water. The oscillation starts after a random motion, and the oscillation pattern apparently depends on the cation species in the water phase. However, a common pattern is included. The cation species only affects the amplitude and frequency and sometimes perturbs the regular pattern owing to the instability at the oil/water interface. This common pattern is explained by a simple model that incorporates the surfactant transport from the droplet to the surrounding water surface. The dependency of the amplitude and frequency on cation species is expressed quantitatively by a single parameter, the product of the amplitude and square of frequency. This parameter depends on the cationic species and can be understood in terms of the spreading coefficient. The simple model successfully explains this dependency.

本研究旨在探讨水面上油滴的振荡现象。油滴中含有一种阴离子表面活性剂，该表面活性剂能够与水中的阳离子发生反应。油滴的振荡始于随机运动之后，其振荡模式显然依赖于水相中的阳离子种类。然而，存在一种普遍的振荡模式。阳离子种类仅影响振幅和频率，有时由于油水界面的不稳定性，会扰动常规的振荡模式。这种普遍的振荡模式可通过一个简单的模型得到解释，该模型考虑了表面活性剂从油滴向周围水表面的传输。振幅和频率对阳离子种类的依赖性通过一个单一参数进行量化，即振幅与频率平方的乘积。该参数依赖于阳离子种类，并可从扩散系数的角度进行理解。该简单模型成功地解释了这种依赖性。