Collaborative Research: ISS: Microgravity enabled studies of particle adsorption dynamics at fluid interfaces

颗粒负载液滴在乳剂、催化、传感、光学材料以及环境修复等方面的应用受到了广泛的关注。形成颗粒负载流体界面的一个重要步骤是颗粒在液滴上的运输和附着（吸附）。不幸的是，直接研究地球上的附着过程与分散在大部分流体中的颗粒的沉降（重力沉降）的竞争效应是具有挑战性的。换句话说，由于重力作用，附着在流体界面上的粒子之间存在竞争并沉降。为了减轻重力的影响，该奖项旨在研究国际空间站微重力条件下颗粒对流体界面的吸附。该项目将阐明在没有沉淀的情况下，颗粒如何附着在液滴上的关键步骤。该奖项的研究结果将引导工程策略，以优化依赖于颗粒负载界面的材料设计。从技术的角度来看，所获得的知识将直接适用于增材制造和光学材料的新兴技术，以影响地球上的生命。颗粒稳定乳剂的稳定性很大程度上取决于界面上颗粒的覆盖率。颗粒吸附过程中的动力学限制限制了皮克林乳液充分发挥其技术潜力。该奖项旨在通过发展：1)流体界面结构-性质（表面压力-面积分数）关系的基本知识，2)理解流体界面从流体到玻璃（缓慢）动力学的转变，以及3)描述扩散限制吸附的验证模型，来推进我们对界面颗粒吸附的理解。该奖项旨在通过在微重力条件下进行实验，了解限制颗粒在流体界面上吸附的机制。微重力实验是必要的，并允许在没有沉淀的情况下研究吸附动力学。梯度扩散到流体界面的时间尺度可能是几个小时，这使得抛物线飞行不是避免重力影响的现实选择。虽然关键实验将在微重力下进行，但这项工作的科学和技术影响将使地球上的生命受益。研究结果将有利于任何涉及颗粒吸附到流体界面的过程，包括制造业、消费品、浮选、石油开采和环境修复。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Particle-laden droplets have received attention for their applications in emulsions, catalysis, sensing, optical materials, as well as environmental remediation. An important step in creating particle-laden fluid interfaces is the transport and attachment (adsorption) of the particles to a fluid droplet. Unfortunately, it is challenging to study directly the attachment process on Earth with the competing effects of sedimentation (gravitational settling) of the particles dispersed in the bulk of the fluid. In other words, there is competition between particles attaching to a fluid interface and settling because of gravity. To alleviate the effect of gravity, this award aims to study adsorption of particles to fluid interfaces under microgravity in the international space station. The project will elucidate the critical steps of how particles attach to droplets in the absence of sedimentation. Findings from this award will lead to engineering strategies to optimize the design of materials that rely on particle-laden interfaces. From a technological standpoint, the knowledge gained will be directly applicable to emerging technologies in additive manufacturing and optical materials to impact life on Earth. The stability of particle-stabilized emulsions strongly depends on the particle coverage at the interface. Kinetic limitations during particle adsorption limit Pickering emulsions from reaching their full technological potential. This award aims to advance our understanding of particle adsorption at interfaces by developing: 1) fundamental knowledge in structure-property (surface pressure-area fraction) relationships at fluid interfaces, 2) an understanding of the transition from fluid to glassy (sluggish) dynamics at fluid interfaces, and 3) a validated model describing diffusion-limited adsorption. This award aims at understanding the mechanisms limiting the adsorption of particles to fluid interface by conducting experiments in microgravity. Microgravity experiments are necessary and allow to investigate adsorption dynamic in the absence of sedimentation. The time scale for gradient diffusion to a fluid interface can be of order of hours, making parabolic flights not a realistic option to avoid gravitational effects. While key experiments will be conducted under microgravity, the scientific and technological impacts of the work will benefit life on Earth. Findings will benefit any processes involving particles adsorption to fluid interfaces including in manufacturing, consumer products, flotation, oil recovery, and environmental remediation.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.