ISS: Collaborative Research: Bimodal Colloidal Assembly, Coarsening and Failure: Decoupling Sedimentation and Particle Size Effects

各种各样的天然和人造材料是由分散在流体中的不同成分组成的，例如颗粒和聚合物分子。例如个人护理产品、食品和墨水。这些产品的物理特性和功能，以及它们的保质期和消费者的认知，都取决于这些组件的行为。因此，设计具有特定所需性能的材料需要更好地了解这些颗粒和聚合物在不同条件下如何相互作用。特别感兴趣的是凝胶状系统，其中粒度变化可能导致产品失效。该奖项将结合计算机模拟和地面实验，以及国际空间站上的实验。目的是研究重力对这些凝胶的影响，并研究尺寸变化对这些材料最终性能的影响。这些发现可以使几个行业受益，也将有助于开辟基础研究的新途径。建议开展一系列外展活动，以加强传统上代表性不足的群体在STEM领域的参与。在这个项目中，我们将研究双峰吸引胶体悬浮液中胶体凝胶、粗化和相分离的物理过程，其中两种粒子群之间的尺寸差异是明显的。这种尺寸差异一方面会导致选择性重力沉降，另一方面会导致大颗粒作为小胶体聚集核的非均匀聚集，导致凝胶变粗和失效。通过解耦重力和粒子间相互作用的作用，探讨粒径差异在胶体凝胶粗化和最终失效中的作用。最终目标是探索颗粒组成（小颗粒与大颗粒的比例）以及颗粒之间相互作用在介导凝胶化，粗化和[重力]失效中的作用范围。除了必要的微重力实验外，还将进行综合努力，通过计算/理论平台结合地面控制实验详细研究物理现象。理论、计算和实验的紧密结合将使我们能够系统地解耦重力和粒径差异在介导凝胶化、粗化和失效中的作用，为理论框架的发展铺平道路，以更好地理解现实世界中应用的有吸引力的胶体系统。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。

A wide range of natural and artificial materials are composed of different components - such as particles and polymer molecules - dispersed in a fluid. Examples are personal care products, food, and inks. Physical properties and function of these products, along with their shelf-life and consumer perception, depend on the behavior of these components. Designing materials with specific desired properties, therefore, requires a better understanding of how these particles and polymers interact under different conditions. Of particular interest are gel-like systems where particle size variations can lead to product failure. This award will combine computer simulations and terrestrial experiments, along with experiments onboard the International Space Station. The goal is to examine the effect of gravity on these gels and to investigate the size variation effects on final properties of such materials. Such findings could benefit several industries and will also help opening new avenues of fundamental research. A series of outreach activities are proposed to enhance the participation of traditionally underrepresented groups in STEM fields.In this project, we will study the physics of colloidal gelation, coarsening and phase-separation in bimodal attractive colloidal suspensions, in which the size difference between the two particle populations is appreciable. This size disparity can cause selective gravitational settling in one hand, and heterogeneous clustering where large particles serve as nuclei for aggregation of small colloids in another hand, leading to coarsening and failure of the gels. The role of particle size difference in coarsening and eventual failure of colloidal gels will be probed by decoupling the role of gravitational forces and inter-particle interactions. The ultimate goal is to explore the role of particle composition (ratio of small to large particles) as well as the range of interactions between the particles in mediating gelation, coarsening, and [gravitational] failure. An integrated effort, with detailed study of the physical phenomena through computational/theoretical platforms in conjunction with control ground experiments in addition to essential micro-gravity experiments will be performed. The cohesive integration of theory, computation and experiments with and without gravity will enable us to systematically decouple the roles of gravity and particle size disparity in mediating gelation, coarsening, and failure, paving the way for the development of a theoretical framework to better understand attractive colloidal systems in real-world applications.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.