Department of Applied Chemistry and Biotechnology , Chiba University , 1-33 Yayoi , Inage, Chiba 263-8522 , Japan.
Department of Basic Science , The University of Tokyo , 3-8-1 Komaba , Meguro, Tokyo 153-8902 , Japan.
Langmuir. 2018 May 15;34(19):5487-5494. doi: 10.1021/acs.langmuir.8b01090. Epub 2018 May 1.
The self-propelled behaviors of macroscopic inanimate objects at surfaces and interfaces are ubiquitous phenomena of fundamental interest in interface science. However, given the existence of a large variety of systems with their own inherent chemical properties, the kinematics of the self-propelled motion and the dynamics of the forces driving these systems often remain largely unknown. Here, we experimentally investigate the spontaneous motion of a sodium oleate tablet at a water-nitrobenzene interface, under nonequilibrium and global isothermal conditions, through measurements of the interfacial tension with the noninvasive, quasi-elastic laser scattering method. The sodium oleate tablet was self-propelled due to an imbalance in the interfacial tension induced by the inhomogeneous adsorption of oleate/oleic acid molecules. The kinetics of the self-propelled motion of a boat-shaped plastic sheet bearing sodium oleate tablets at a sodium oleate aqueous solution-nitrobenzene interface was also studied. The interfacial tension difference between the front and rear of the boat was quantitatively identified as the force pushing the boat forward, although the Marangoni flow due to the uneven distribution of the interfacial tension behind the boat tended to decelerate the motion.
在表面和界面处，宏观无生命物体的自主运动是界面科学中具有基本兴趣的普遍现象。然而，鉴于存在具有自身固有化学性质的各种系统，自主运动的运动学和驱动这些系统的力的动力学通常仍然很大程度上未知。在这里，我们通过使用非侵入性的、准弹性激光散射方法测量界面张力，在非平衡和整体等温条件下，实验研究了油酸钠片剂在水-硝基苯界面处的自发运动。由于油酸盐/油酸分子的不均匀吸附引起的界面张力不平衡，油酸钠片剂自行推进。还研究了在油酸钠水溶液-硝基苯界面处承载油酸钠片剂的船形塑料片的自主运动的动力学。定量确定了船首和船尾之间的界面张力差作为推动船前进的力，尽管由于船尾后面的界面张力不均匀分布导致的马拉高尼流倾向于使运动减速。
