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由分散在流体中的不同成分组成，如颗粒和聚合物分子。例如个人护理产品、食品和墨水。这些产品的物理属性和功能，以及它们的保质期和消费者感知，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是如何相互作用的。特别令人感兴趣的是凝胶状系统，其中颗粒大小的变化可能导致产品故障。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。我们的目标是研究重力对这些凝胶的影响，并调查尺寸变化对此类材料最终性能的影响。这些发现可能会让几个行业受益，也将有助于开辟基础研究的新途径。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化、粗化和相分离的物理，其中两个粒子群体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的核心，导致凝胶粗化和失效。颗粒大小差异在胶体凝胶粗化和最终失效中的作用将通过分离重力和颗粒间相互作用的作用来探讨。最终目标是探索颗粒组成(小颗粒与大颗粒的比例)以及颗粒之间的相互作用在调节胶凝、粗化和[重力]破坏中的作用。除了基本的微重力实验外，还将进行综合努力，通过计算/理论平台结合地面控制实验对物理现象进行详细研究。在有重力和无重力的情况下，理论、计算和实验的紧密结合将使我们能够系统地分离重力和颗粒大小差异在调节胶凝、粗化和失效中的作用，为开发理论框架以更好地了解现实世界应用中有吸引力的胶体系统铺平道路。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势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.