New theoretical and simulation approach for understanding packing structures of soft self-adjusting objects

在设计新的实体材质时，重要的是要处理材质的组成对象如何组合在一起，以根据应用程序调整属性。使用热处理或施加外力可以改变这种填料，从而改变材料的结构以适应开发商的需要。例如，这种类型的操作用于控制玻璃、钢和塑料的属性。许多用于预测这些堆积排列的传统计算机模拟方法假定对象是坚硬的球体。但真正的材料通常是由柔软的物体制成的。这些包装将不同，就像气球的包装与保龄球不同。该奖项使用了一种新的计算机模型来了解如何控制粘稠的聚合物对象的包装。将聚合物硬度和加工条件与整体材料性能联系起来，将为设计材料的更快发展提供新的机会。该奖项旨在测试一种材料的填充结构与颗粒体积分数(目前的普遍解释)关系不大，而更多地与可变形颗粒的表面积有关的假设。这些模拟基于一个顶点模型，在该模型中，表面之间的接触几何关系决定了物理交互。第一个目标是量化热波动、颗粒表面张力和颗粒之间的材料交换在确定结构的平衡偏好中的作用。第二个目标是了解时间的动态演变。这包括在熄灭无序状态时形成有序状态，以及有序状态之间的跃迁。2D模拟代表薄膜，而3D模拟代表大块材料。该模型的粗粒度性质使得包括晶粒度和晶界的影响在内的大型组装成为可能。该奖项将培训本科生和研究生以及博士后研究人员将计算机模拟应用于材料。它还将创建一个互动的在线工具，通过学习材料特性和设计来帮助学生追求STEM职业生涯。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。

When designing new solid materials, it is important to manipulate how a material’s constituent objects pack together to tailor the properties to an application. Using heat treatment or applying an external force can change this packing, thereby modifying the material’s structure to fit the developer’s need. For example, this type of manipulation is used to control properties of glass, steel, and plastics. Many conventional computer simulation methods used to predict these packing arrangements assume that the objects are hard spheres. But often real materials are made of soft objects. These will pack differently, like how balloons pack differently from bowling balls. This award uses a new computer model to understand how to control the packing of squishy polymeric objects. Connecting the polymer stiffness and processing conditions with the overall material properties will enable new opportunities for faster development of designer materials.This award aims to test the hypothesis that the packing structures observed for a material have less to do with the volume fraction of particles (the current common interpretation) and more to do with the surface area of the deformable particles. The simulations are based on a vertex model in which the geometry of contact between surfaces determines the physical interactions. The first objective is to quantify the roles of thermal fluctuations, particle surface tension, and exchange of material between particles in determining the equilibrium preferences for structures. The second objective is to understand the dynamic evolution in time. This includes the formation of ordered states upon quenching a disordered state, as well as transitions between ordered states. 2D simulations represent thin films while 3D simulations represent bulk materials. The coarse-grained nature of the model enables large assemblies including the effects of crystal grain size and grain boundaries. The award will train undergraduate and graduate students as well as a postdoctoral researcher in the application of computer simulations to materials. It will also create an interactive online tool to help motivate students to pursue STEM careers via learning about material properties and design.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.