OASIS - Smectic Films under Microgravitation

作为绿洲实验(空间近晶岛的观测和分析)[1]的一部分，在国际空间站上与国际伙伴合作，在微重力条件下研究了近晶膜。国际空间站的实验于2015年7月至2016年3月进行。他们提供了自2017年以来向合作伙伴提供的大规模、高质量的独特数据。实验包括准二维(2D)液体中夹杂物的观察、相互作用的表征、有序结构自发形成的研究和热毛细管实验。在失重状态下自动生成球状近晶薄膜(气泡)，并形成岛状(多层附加分子层)和液滴(透镜状液体包裹体)形式的夹杂物。微重力(µg)是防止物体在重力场中沉积在球状气泡表面所必需的。在观测对象的局部尺度上，曲率可以忽略不计。用光学相机进行了长期实验，观察了胶片平面内的流体动力学过程。需要进一步研究的有趣现象包括包裹体的相互作用，包括它们的合并，以及它们形成的集体结构的长期稳定性。迄今为止非常成功的国际空间站飞行数据的评估将继续进行，并通过正常重力下的实验进行补充。主要目标是研究薄膜中液滴的自组织，各向同性相和向列相中液滴合并的动力学，以及二维乳液老化(Ostwald熟化)的分析和模拟。在抛物线飞行上进行了更短时间窗口的进一步微格实验。我们研究了自由漂浮的闭合近晶薄膜。这类物体的形状动力学代表了泡泡和肥皂泡行为之间的中间情况。在短时间尺度上，薄膜的有效表面张力像囊泡一样消失。它们形成独特的褶皱结构，否则只能在非常粘稠或固体的薄膜中观察到。本文计划的研究目的是对这种褶皱进行表征和建模，以获得关于液体薄膜形状动力学的基本知识，并获得迄今很少被研究的近晶相的材料参数，如近晶层的柔韧性。计划进行另一次抛物线飞行。

As part of the OASIS experiment (Observation and Analysis of Smectic Islands in Space) [1], smectic films were examined under microgravity on the ISS in cooperation with international partners. The ISS experiments took place from July 2015 to March 2016. They provided unique data on a large scale and in high quality, which are available to the cooperation partners since 2017. These data are cooperatively evaluated.The experiments included the observation of inclusions in quasi-two-dimensional (2D) liquids, the characterization of their interactions, the investigation of the spontaneous formation of ordered structures and thermocapillary experiments. Smectic films in spherical geometry (bubbles) were automatically generated in weightlessness, and inclusions in the form of islands(Layers of additional molecular layers) and drops (lenticular liquid inclusions) were prepared.Microgravity (µg) is indispensable to prevent sedimentation of the objects on the spherical bubble surface in the gravitational field. On the local scale of the observed objects, curvature is negligible. The hydrodynamic processes in the film plane were observed in long-term experiments with optical cameras. Interesting phenomena that require further investigation include the interactions of inclusions, including their merging, as well as the long-term stability of the collective structures they form.The evaluation of the data from the ISS flight, which has been very successful so far, is to be continued and supplemented by experiments under normal gravity. The primary goals are the investigation of the self-organization of drops in thin films, the dynamics of the merging of drops in the isotropic and the nematic phases, as well as the analysis and modeling of aging of two-dimensionalemulsions (Ostwald ripening).Further µg experiments with a shorter time window were carried out on parabolic flights. We investigated free-floating closed smectic films. The shape dynamics of such objects represent an intermediate case between the behavior of vesicles and soap bubbles. On short time scales, the films have a vanishing effective surface tension like vesicles. They form unique wrinkling structures that are otherwise only observable in very viscous or solid films. The aims of the investigations planned here are the characterization of such wrinkling and their modeling to derive fundamental knowledge about the shape dynamics of thin liquid films, and access to so far hardly investigated material parameters of smectic phases such as the flexibility of smectic layers. Another parabolic flight is planned.