Abstract：
OBJECTIVE: In order to understand the basic mechanisms affecting emulsion stability, the intrinsic dynamics of the drop population must be investigated. We hypothesize that transient ballistic motion can serve as a marker of interactions between drops. In 1G conditions, buoyancy-induced drop motion obscures these interactions. The microgravity condition onboard the International Space Station enable this investigation.
METHODS: We performed Diffusing Wave Spectroscopy (DWS) experiments in the ESA Soft Matter Dynamics (SMD) facility. We used Monte Carlo simulations of photon trajectory to support data analysis. The analysis framework was validated by ground-based characterizations of the initial drop size distribution (DSD) and the properties of the oil/water interface in the presence of surfactant.
RESULTS: We characterized the drop size distribution and found to be bi-disperse. Drop dynamics shows transient ballistic features at early times, reaching a stationary regime of primarily diffusion-dominated motion. This suggests different ageing mechanisms: immediately after emulsification, the main mechanism is coalescence or aggregation between small drops. However at later times, ageing proceeds via coalescence or aggregation of small with large drops in some emulsions. Our results elucidate new processes relevant to emulsion stability with potential impact on industrial processes on Earth, as well as enabling technologies for space exploration.
METHODS: We performed Diffusing Wave Spectroscopy (DWS) experiments in the ESA Soft Matter Dynamics (SMD) facility. We used Monte Carlo simulations of photon trajectory to support data analysis. The analysis framework was validated by ground-based characterizations of the initial drop size distribution (DSD) and the properties of the oil/water interface in the presence of surfactant.
RESULTS: We characterized the drop size distribution and found to be bi-disperse. Drop dynamics shows transient ballistic features at early times, reaching a stationary regime of primarily diffusion-dominated motion. This suggests different ageing mechanisms: immediately after emulsification, the main mechanism is coalescence or aggregation between small drops. However at later times, ageing proceeds via coalescence or aggregation of small with large drops in some emulsions. Our results elucidate new processes relevant to emulsion stability with potential impact on industrial processes on Earth, as well as enabling technologies for space exploration.
摘要：
目的：为了了解影响乳液稳定性的基本机制，必须调查液滴种群的内在动态。我们假设瞬态弹道运动可以作为液滴之间相互作用的标记。在1G条件下，浮力引起的下降运动掩盖了这些相互作用。国际空间站上的微重力条件使这项调查成为可能。
方法：我们在ESA软物质动力学（SMD）设施中进行了扩散波谱（DWS）实验。我们使用光子轨迹的蒙特卡罗模拟来支持数据分析。通过在表面活性剂存在下初始液滴尺寸分布（DSD）和油/水界面特性的地面表征，验证了分析框架。
结果:我们表征了液滴尺寸分布并发现是双分散的。液滴动力学在早期显示出瞬态弹道特征，达到主要是扩散主导运动的平稳状态。这表明不同的老化机制：乳化后立即，主要机制是小液滴之间的聚结或聚集。然而，在以后的时间里，老化通过一些乳液中小滴与大滴的聚结或聚集进行。我们的结果阐明了与乳液稳定性相关的新工艺，并对地球上的工业过程产生潜在影响。以及支持太空探索的技术。
方法：我们在ESA软物质动力学（SMD）设施中进行了扩散波谱（DWS）实验。我们使用光子轨迹的蒙特卡罗模拟来支持数据分析。通过在表面活性剂存在下初始液滴尺寸分布（DSD）和油/水界面特性的地面表征，验证了分析框架。
结果:我们表征了液滴尺寸分布并发现是双分散的。液滴动力学在早期显示出瞬态弹道特征，达到主要是扩散主导运动的平稳状态。这表明不同的老化机制：乳化后立即，主要机制是小液滴之间的聚结或聚集。然而，在以后的时间里，老化通过一些乳液中小滴与大滴的聚结或聚集进行。我们的结果阐明了与乳液稳定性相关的新工艺，并对地球上的工业过程产生潜在影响。以及支持太空探索的技术。
