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Study on Marangoni instabilities of condensed domains of Langmuir monolayers

Langmuir单层凝聚域Marangoni不稳定性研究

基本信息

批准号：
18560018
负责人：
HATTA Eiji
金额：
$ 2.43万
依托单位：
Hokkaido University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2006
资助国家：
日本
起止时间：
2006 至 2007
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-18560018/
关键词：
Langmuir monolayer Brewster angle microscopy Marangoni instability Optical tweezers Local heating Nonequilibrium growth of domains 光ビンセット非平行成長

项目摘要

We developed a combined system of Brewster angle microscopy with laser tweezers. This system enables one to initiate and to observe the nonequilibrium, Marangoni-driven directional growth of condensed domains of Langmuir monolayers in the field of view of the monitor upon local laser heating on them. By using the system directional growth of condensed domains on the water surface is found to be classified mainly by two types of morphologies. One is fractal domain, and the other is dendrite structure. In the latter one, side branches on one side to the main branch were selectively grown, I.e., asymmetric dendritic growth was realized. The breaking of symmetry in the growth of side branches is correlated with the growth direction and velocity of the neighboring branches approaching the side branches. Moreover, dendritic growth is triggered by the existence of neighboring branches and exhibits a variety of interfacial instabilities of growing domains. As the results of directional growth instabilities, the transient growth of curved tips of domains and wavy boundaries between grown domains were observed. Such Marangoni-driven growth instabilities of non-equilibrium directional domains can be caused by I) the competitive capture of amphiphilic molecules in the subphase and/or at the interface in the supersaturated LE phase between the neighboring domains in the simultaneous growth of high density of directional arrays of dendritic domains and by ii) electrostatic repulsion between the neighboring condensed domains. The cooperative effect of the competitive capture and the electrostatic repulsion of molecules between the neighboring domains on the Marangoni-driven, directional growth of condensed domains thus affects the growth rate of individual domains effectively and leads to the intriguing modulated domain patterns.

我们研制了一套布鲁斯特角显微镜与激光光镊的组合系统。该系统使一个启动和观察的非平衡，马兰哥尼驱动的朗缪尔单层的凝聚域的定向生长在监视器的视野后，对他们进行局部激光加热。通过使用该系统的定向生长的凝聚域在水面上被发现主要分为两种类型的形态。一种是分形畴，另一种是枝晶结构。在后者中，选择性地生长主分支一侧的侧枝，即，实现了不对称枝晶生长。侧枝生长的对称性破缺与邻近侧枝的生长方向和生长速度有关。此外，枝晶生长是由相邻分支的存在引发的，并表现出多种生长域的界面不稳定性。作为定向生长不稳定性的结果，观察到了畴尖端弯曲和畴间波状边界的瞬态生长。非平衡定向畴的这种马兰哥尼驱动的生长不稳定性可以由以下引起：I）在树枝状畴的高密度定向阵列的同时生长中，相邻畴之间的亚相中和/或过饱和LE相中的界面处两亲分子的竞争性捕获，以及ii）相邻凝聚畴之间的静电排斥。竞争性捕获和相邻畴之间的分子的静电排斥对凝聚畴的Marangoni驱动的定向生长的协同作用，从而有效地影响单个畴的生长速率，并导致有趣的调制畴图案。