CAREER: Jamming in Flexible Geometries-from Shape Sculpting to Shapeshifting

该职业奖支持卡死软材料的理论研究、教育和推广。沙子、玻璃、泡沫和胶体等材料会随着密度的增加而变得坚硬或堵塞。如果施加足够的力，卡住的材料具有脆性和易流动等显著特性。这些特性是由于它们的结构：处于堵塞状态的粒子只有最小数量的邻居来保持它们的位置。PI将研究当系统发生形状变化时，如在液滴或弹性体上，干扰过程是如何改变的。更好的理解将有助于在软机器人、药物输送系统、致动器和人造肌肉等应用中创造出利用形状的材料和设备。PI将开发一个柔性几何干扰的计算模型，并使用它来确定粒子和初始形状如何影响结构，以及如何通过仔细选择系统的组件来雕刻所需的最终形状。通过在模拟中加入对外部影响做出反应的粒子，比如对应用领域的反应，或者在自己的力量下移动，研究团队将确定如何使用这些粒子来制造可以自发改变形状的变形材料。作为该项目的一部分开发的计算机软件将通过公共存储库向社区完全开放。该奖项还支持与研究密切相关的外展和教育工作。教育部分旨在通过将基于研究的项目和活动纳入PI新开发的计算物理课程，将软物质和计算结合起来。外联部分将制作和传播一款网页游戏，连同教师开发的课堂材料，向高中生和公众传播干扰。该奖项还将支持聋人和重听学生参加塔夫茨大学的夏季研究，他们将进行模拟和分析，以支持这项研究。该职业奖支持卡死软材料的理论研究、教育和推广。堵塞是在颗粒状介质中发生的向刚性的过渡。该研究的目标是通过计算机模拟了解当干扰发生在柔性几何中时，干扰过渡是如何被修改的。该建议的中心假设是，在柔性几何中的阻塞状态构成了一种新的阻塞类别，称为“度量阻塞”，其中系统在表面的集体运动和流形的变形方面都是稳定的。了解当形状和顺序共同进化时如何修改物理效应（如干扰），为这些过程提供了基本的见解，并将使新材料、设备和工业技术（如软机器人、药物输送系统、致动器和利用结果的人造肌肉）的创造成为可能。为了验证中心假设，PI将创建一个度量干扰过程的计算模型，并使用它来：i)确定形状和粒子如何控制度量阻塞状态的特性；Ii)确定柔性几何形状如何影响度量干扰，以及如何使用它来雕刻所需形状的软胶体颗粒；Iii)将可动粒子和活性粒子纳入模型，以确定如何使用这些粒子来创建可以自发改变形状的变形材料。这项工作将通过提供对二维和三维新度量阻塞状态的物理的详细理解，秩序和形状变化之间的联系，可以从这些过程中出现的形状，以及微观结构变化如何诱导形状演变，有助于推进软物质领域。为了帮助其他人驾驭这类材料所固有的众多复杂的物理效应，该研究还将提供开源计算工具来促进这种设计。该奖项还支持与研究密切相关的外展和教育工作。教育部分旨在通过将基于研究的项目和活动纳入PI新开发的计算物理课程，将软物质和计算结合起来。外联部分将制作和传播一款网页游戏，连同教师开发的课堂材料，向高中生和公众传播干扰。该奖项还将支持聋人和重听学生参加塔夫茨大学的夏季研究，他们将进行模拟和分析，以支持这项研究。

NONTECHNICAL SUMMARYThis CAREER award supports theoretical research, education and outreach on jammed soft materials. Materials such as sand, glasses, foams and colloids can become rigid or jam as the density is increased. Jammed materials possess remarkable properties such as fragility and flowing readily if sufficient force is applied. These properties are due to their structure: particles in a jammed state have only the minimum number of neighbors required to hold them in place. The PI will investigate how the jamming process is altered when it occurs in a system that is changing shape, such as on a fluid droplet or an elastic body. A better understanding would enable the creation of materials and devices in applications that exploit shape, such as soft robotics, drug delivery systems, actuators, and artificial muscles. The PI will develop a computational model of jamming in flexible geometries and use it to determine how particles and initial shape affect the structure and how desired final shapes can be sculpted by carefully choosing the components of the system. By incorporating particles in the simulation that respond to external influences, such as in response to an applied field, or move under their own power, the research team will determine how these particles can be used to create shape-shifting materials that can change shape spontaneously. Computer software developed as part of this project will be made fully accessible to the community on public repositories.This award also supports outreach and education efforts that are closely integrated with the research. The educational component aims to integrate soft matter and computation by incorporating projects and activities based on the research into the PI's newly developed course in Computational Physics. The outreach component will create and disseminate a web game, together with classroom materials developed by teachers, that communicates jamming to high school students and the general public. This award will also support the participation of Deaf and Hard of Hearing students in summer research at Tufts who will conduct simulations and analysis in support of the research. TECHNICAL SUMMARYThis CAREER award supports theoretical research, education and outreach on jammed soft materials. Jamming is a transition to rigidity that occurs in granular media. The goal of the research is to understand by computer simulations how the jamming transition is modified when it occurs in a flexible geometry. The central hypothesis of the proposal is that jammed states in flexible geometries constitute a new jamming category called "metric jammed" where the system is stable both with respect to collective motions of the surface and deformations of the manifold. Understanding how physical effects such as jamming are modified when shape and order co-evolve provides fundamental insight into these processes and will enable the creation of new materials, devices and industrial techniques such as soft robotics, drug delivery systems, actuators and artificial muscles that exploit the results. To test the central hypothesis, the PI will create a computational model of the metric jamming process and use this to: i) determine how shape and particles control the properties of the metric jammed state; ii) identify how flexible geometries affect metric jamming and how this can be used to sculpt soft colloidal particles of a desired shape; iii) incorporate actuatable and active particles into the model to determine how such particles can be used to create shape-shifting materials that can change shape spontaneously. This work will help advance the field of soft matter by providing a detailed understanding of the physics of the new metric jammed state in both two and three dimensions, the connections between order and shape change, the shapes that can emerge from these processes, and how microstructural changes can induce shape evolution. To help others navigate the numerous and complex physical effects intrinsic to this class of materials, the research will also provide open-source computational tools to facilitate this design.This award also supports outreach and education efforts that are closely integrated with the research. The educational component aims to integrate soft matter and computation by incorporating projects and activities based on the research into the PI's newly developed course in Computational Physics. The outreach component will create and disseminate a web game, together with classroom materials developed by teachers, that communicates jamming to high school students and the general public. This award will also support the participation of Deaf and Hard of Hearing students in summer research at Tufts who will conduct simulations and analysis in support of the research.