Reconfigurable Active Matter

该奖项支持理论，计算和数据密集型研究和教育，重点是可重构活性材料的设计。当一个人想到介质中的分子或纳米粒子时，脑海中会浮现出漫无目的地移动和振动的非常小的物体。在过去的十年中，人们发现可以通过化学方法改变纳米颗粒的表面，这样它们就可以利用周围环境中的化学能，它们就像微观引擎一样工作。因此，它们可以以非常高的速度和可控的方式穿过细菌等介质。这一突破导致了一个新的研究领域的出现，今天被称为活性物质，包括对人造和生物微观系统的研究。由于与生物系统的直接类比，活化的纳米颗粒组通常被称为合成的“生命”系统，它们的集体行为确实让人想起群集的细菌或鸟群所表现出的行为。这些纳米粒子最吸引人的特点之一是，它们可以制成任意复杂的形状，并且具有广泛的相互作用和速度，可以通过将它们暴露在蓝光下来打开和关闭。 该项目的想法是使用理论和尖端数值和数据科学策略的组合，包括机器学习，来研究活性粒子组装的特性。目标是设计这些粒子应该如何放在一起或相互连接，以便它们可以形成功能性的微观物体。因此，PI的目标是研究如何创造微观“机器”，不仅可以快速通过介质，而且还可以获得特定的形状，并且像蛋白质一样，随着时间的推移以可控的方式改变它们的形状。这用于定义术语"可重构活性材料"。如果成功，该项目将有助于开发强大的策略，以设计下一代智能材料，这些材料由微观活性机器构建，通过活性纳米颗粒的自发组装而成。可重构活性材料在我们日常生活中的应用不计其数，涵盖了从刺激响应材料或传感器到组织修复和伤口愈合设备的各个领域。更一般地说，它们可能在纳米医学领域开辟新的机会。该项目包括教育活动，包括培训本科生和研究生，指导博士后研究员，以及与致力于提高妇女地位的校内组织和其他在科学领域代表性不足的群体合作。该奖项支持理论，计算和数据密集型研究和教育，旨在从自推进纳米粒子设计可重构的主动组件。活性系统的特征是其组成部分的非平衡性质，这导致了一种非凡的现象学复杂性，在平衡热力学领域没有等价物。自推进粒子的集体行为的研究是主动系统最简单的实现之一，一直处于最近理论研究的前沿。为研究这些合成单位而开发的想法和理论框架在几个生物系统中找到了肥沃的土壤，这些生物系统也固有地失去了平衡，或者发生在可能发生显著活跃波动的环境中。PI计划使用理论方法和数值模拟相结合的方法来开发合理的设计策略，以基于自推进粒子的受控组装来设计可重构的活性材料。 这将通过研究流体动力学相互作用在活性剂如何相互作用以及在表面和胶体笼附近或在限制介质中的行为中发挥的作用来实现，并利用它来设计可重构的活性簇。受最近4D打印实验的启发，PI还将探索一种结构形成和主动可重构性的替代途径，该途径不依赖于自组装，而是依赖于线性连接的主动胶体游泳者的折叠动力学。在一组线性或二维受限的活性粒子中，活性力和弹性力之间的耦合为实现无需自组装的可重构性目标提供了尚未开发的潜力，并导致了与蛋白质折叠设计和DNA折纸物理学的有趣类比。PI预计，该项目的成果将有助于推进平衡统计力学，并为自下而上组装主动可重构结构的设计策略提供见解。PI将在这项研究活动中开发的工具和理论方法应易于应用或扩展到其他活性系统，并可能对依赖于类似物理机制的生物学问题（如组织修复和伤口愈合）以及纳米医学产生重要影响。该项目有助于本科生和研究生的教育。目前正在与哥伦比亚的校园组织"妇女参与科学"合作实施一项外联计划，该组织致力于提高妇女和代表性不足的人口在科学、技术、工程和数学领域的地位，该奖项反映了NSF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进行评估，被认为值得支持审查标准。

NONTECHNICAL SUMMARYThis award supports theoretical, computational, and data-intensive research and education and education that focuses on the design of reconfigurable active materials. When one thinks about molecules or nanoparticles in a medium, very small objects that aimlessly move and vibrate come to mind. Over the past decade, it has been discovered that it is possible to chemically alter the surface of nanoparticles so that they can utilize chemical energy in their surroundings, and they act like microscopic engines. Thus powered, they can run through a medium like bacteria at very high speeds, and in a controllable manner. This breakthrough resulted in the emergence of a new field of research that is today called active matter and includes the study of both man-made and biological microscopic systems. Because of the direct analogy with biological systems, groups of activated nanoparticles are often referred to as synthetic "living" systems, and their collective behavior is indeed reminiscent of that exhibited by swarming bacteria or flocks of birds. One of the most appealing features of these nanoparticles is that they can be made into arbitrarily complex shapes, and with a wide range of mutual interactions and speeds that can be turned on and off by exposing them to blue light. The idea of this project is to use a combination of theoretical and cutting-edge numerical and data-science strategies, including machine learning, to study the properties of assemblies of active particles. The goal is to design how these particles should be put together or linked to each other so that they can form functional microscopic objects. So, the PI aims at studying how to create microscopic “machines” that can not only quickly move through a medium, but also acquire specific shapes, and, like proteins, change their shape over time in a controllable fashion. This serves to define the term "reconfigurable active materials". If successful, this project will help enable the development of robust strategies to design the next generation of smart materials built from microscopic active machines that are put together by spontaneous assembly of active nanoparticles. The applications of reconfigurable active materials in our daily life are countless, and cover areas ranging from stimuli-responsive materials, or sensors, to tissue repair and wound healing devices. More generally, they may open new opportunities in the field of nanomedicine. This project includes educational activities, including training undergraduate and graduate students, mentoring postdoctoral research fellows, and collaboration with on-campus organizations dedicated to the advancement of women and other groups that are underrepresented in science. TECHNICAL SUMMARYThis award supports theoretical, computational, and data-intensive research, and education with the aim of designing reconfigurable active assemblies from self-propelled nanoparticles. Characteristic of active systems is the out-of-equilibrium nature of its constituent parts which results in a phenomenological complexity that is extraordinary and has no equivalent in the realm of equilibrium thermodynamics. The study of the collective behavior of self-propelled particles, one of the simplest realizations of an active system, has been at the forefront of recent theoretical efforts. Ideas, and theoretical frameworks that have been developed to study these synthetic units have found fertile ground in several biological systems which are also inherently out of equilibrium, or occur in an environment where significant active fluctuations can occur. The PI plans to use a combination of theoretical approaches and numerical simulations to develop rational design strategies to engineer reconfigurable active materials based on the controlled assembly of self-propelled particles. This will be achieved through investigating the role that hydrodynamic interactions can play in how active agents interact with each other and behave when near surfaces and colloidal cages, or in confining media, and harnessing it to design reconfigurable active clusters. Inspired by recent experiments on 4D printing, the PI will also explore an alternative path towards structure formation and active reconfigurability that does not rely on self-assembly, but on the folding dynamics of linearly connected active colloidal swimmers. The coupling between active and elastic forces developing within a linearly, or two-dimensionally, constrained set of active particles provides untapped potential towards the goal of reconfigurability without self-assembly, and leads to intriguing analogies with protein folding design and the physics of DNA origami. The PI anticipates that the outcomes of this project will help advance out-of-equilibrium statistical mechanics and provide insights into design strategies for bottom-up assembly of active reconfigurable structures. The tools and theoretical approaches that the PI will develop in this research activity should be easily applicable or extended to other active systems, and may have important implications for biological problems that rely on similar physical mechanisms, such as tissue repair and wound healing, and in nanomedicine. This project contributes to the education of undergraduate and graduate students. An outreach plan in collaboration with the on-campus organization Women in Science at Columbia, whose efforts are dedicated to the advancement of women and underrepresented populations in science, technology, engineering, and mathematics is currently underway, and will be continued and extended.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.