Probing 2-D Coalescence and Aggregation with Tunable Paramagnetic Colloidal Clusters

CBET -1705703 PI：Biswal，Sibani L.液滴的聚结和胶体颗粒的聚集在材料加工应用和自然发生的过程中很重要。 对于自由悬浮在散装液体中的液滴和颗粒，已经广泛地研究了聚结和聚集。 该奖项将支持对局限于表面的胶体颗粒聚集的研究。 在这种情况下，聚集的动力学预计将从根本上不同于散装颗粒的聚集。 研究聚集的关键挑战是控制颗粒之间可能导致聚集的力。 在这个项目中，这个挑战将通过使用超顺磁性粒子簇并将系统置于旋转磁场中来解决。 胶体团簇的聚集将在团簇之间的力可以调节并且始终已知的条件下进行检查。 将研究团簇聚集的动力学、团簇内颗粒排列的变化以及聚集后得到的结构。 这些结果将对材料科学家和工艺工程师有用，他们正在开发具有独特电子，光学或催化性能的新二维材料。 它还将为其他具有界面或晶界的工程材料提供新的见解，这些界面或晶界会影响材料的加工和可靠性。 该项目将吸引不同学术水平的学生，包括参加赖斯暑期项目的社区大学生。 将为当地高中生开发磁性胶体悬浮液独特性能的演示。该奖项将支持二维胶体团簇聚结和聚集的实验研究。 簇将由分散在水溶液中的微米级超顺磁性胶体颗粒组成。将施加高频旋转磁场，从而在顺磁性胶体之间产生长距离、各向同性的吸引相互作用势，可以通过改变磁场强度从3 kBT精确调谐到40 kBT。 这些实验将确定干涉势如何影响线张力和界面厚度等特性。该实验将被设计为监测聚结和聚集作为相互作用势的函数，并了解在集群组装过程中空隙空间如何退火。最后，该项目将集中在二维系统中的向错和缺陷的形成及其对二维集群动力学的影响。

CBET - 1705703PI: Biswal, Sibani L.Coalescence of liquid droplets and aggregation of colloidal particles are important in materials processing applications and in naturally-occurring processes. Coalescence and aggregation have been studied extensively for droplets and particles that are freely suspended in bulk liquids. This award will support research into aggregation of colloidal particles that are confined to a surface. The dynamics of aggregation in this case are expected to be fundamentally different than aggregation of particles in the bulk. The key challenge in studying aggregation is to control the forces between particles that can lead to aggregation. In this project, that challenge will be addressed by using clusters of superparamagnetic particles and placing the system in a rotating magnetic field. The aggregation of the colloidal clusters will be examined under conditions where the forces between the clusters can be tuned and are known at all times. The dynamics of cluster aggregation, changes in the arrangement of particles within the clusters, and the resulting structure that is obtained after aggregation will be studied. The results will be useful to material scientists and process engineers who are developing new two-dimensional materials that have unique electronic, optical, or catalytic properties. It will also provide new insight into other engineered materials that have interfaces or grain boundaries that can affect materials processing and reliability. The project will engage students at various academic levels, including community college students who participate in a summer program at Rice. Demonstrations of the unique properties of magnetic colloidal suspensions will be developed for local high-school students.This award will support an experimental study of coalescence and aggregation of two-dimensional colloidal clusters. The clusters will consist of micron-sized superparamagnetic colloidal particles dispersed in aqueous solution. A high frequency rotating magnetic field will be applied, resulting in a long-range, isotropic attractive interaction potential between the paramagnetic colloids that can be precisely tuned from 3kBT to 40kBT by varying the strength of the magnetic field. The experiments will determine how the interactional potential influences properties such as line tension and interfacial thickness. The experiment will be designed to monitor coalescence and aggregation as a function of interaction potential and to understand how void spaces are annealed during the assembly of clusters. Finally, the project will focus on the formation of disclinations and defects in two-dimensional systems and their implications on two-dimensional cluster dynamics.