RHEOLOGY, ENTROPY PRODUCTION AND RATCHETING OF DEFORMABLE ACTIVE SYSTEMS

可变形主动系统的流变学、熵产生和棘轮

• 批准号: 2321925
• 负责人: Angelo Cacciuto
• 金额: $ 34.49万
• 依托单位: Columbia University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2024
• 资助国家: 美国
• 起止时间: 2024-01-01 至 2026-12-31
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2321925&HistoricalAwards=false
• 关键词: RHEOLOGY; ENTROPY; PRODUCTION; RATCHETING; DEFORMABLE

NON-TECHNICAL SUMMARY This award supports theoretical research and education that aims at understanding three important aspects of active materials that are currently unexplored. Active matter is an exciting new field in materials engineering and has come into prominence over the last decade. This occurred because of the development of micro-particles capable of self-propulsion. One can think of these particles as synthetic analogs of bacteria whose shape, surface chemistry and velocity can be designed in a lab. There are several fundamental questions that need to be addressed in this field and that offer new opportunities for the development of the next generation of smart materials. What is the elastic response to external stimuli of materials formed by active particles? This is an important problem that can improve our understanding of the mechanical properties of a large number of materials, from biofilms to epithelial tissue. Another unexplored issue concerns the behavior of active surfaces. Unlike synthetic vesicles, the motion of a biological cell is completely determined by complex biochemical reactions. This makes their behavior similar to that of active systems. It is therefore important to understand how surfaces/vesicles respond to active forces. For instance, fibroblasts and epithelial cancerous cells can acquire directional motion when confined within rigid, asymmetric micro-channels. The PI will explore to what extent such a behavior can be captured by a much simpler system: a synthetic vesicle loaded with active particles. The goal is to develop simple synthetic analogs of biological cells capable of mimicking their mechanical behavior. Finally, one of the main characteristics of active systems is that they break time-reversal symmetry, i.e. running time backwards on a particle trajectory does take the particle back along the same path from which it came. The degree to which this happens in a system can be quantified by measuring Entropy Production. The team will measure this quantity for a number of active systems and establish a link between spatial gradients in Entropy Production and the degree to which active systems are out of equilibrium and capable of performing work. The outcomes of this research will provide insight into how to design stimuli-responsive materials capable of performing work at the microscale. The numerical tools developed for this project should be transferable to other active systems and will have important implications for a number of biological problems that rely on similar physical mechanisms. The award contributes to the education of undergraduate and graduate students which the PI will recruit to participate in these projects, and they will have first-hand exposure to cutting-edge numerical and statistical methods to model active systems. Furthermore, an outreach plan in collaboration with a number of on-campus organizations such as WISC (Women in Science at Columbia), whose efforts are dedicated to the advancement of women and underrepresented minorities in the sciences, technology, engineering and math, is currently underway, and will be further extended.TECHNICAL SUMMARYThis award supports theoretical research and education that aims at understanding three important issues of active materials that are currently unexplored. The first issue concerns the rheological properties of active condensates. Although a large body of work has been devoted to studying self-assembly, dynamics and the phase behavior of active colloidal particles, limited work has been done to understand the elastic properties of active condensates and their response to external stimuli. This is a fundamental problem that needs to be addressed to better characterize the mechanical properties of these materials. The second issue concerns the interplay between elastic and active forces on fluid vesicles using models that allow for topological transitions. The PI will explore under what conditions rectification can occur when giant unilamellar vesicles are loaded with active particles. While a good amount of work has been done to understand motion rectification of single active particles, not much is known about the transport properties of soft, deformable interfaces activated by self-propelling particles across micro-channels. This is an important problem given that fibroblasts and epithelial cancerous cells can acquire directional motion when confined within asymmetric, periodic channels, and would present a minimal model for the description of such a complex system. The third issue deals with a fundamental question about the very nature of active systems. Although the most intriguing phenomenological behavior of active systems arises, at the most fundamental level, because of time-reversal symmetry breaking, and entropy production is the hallmark signature of lack of equilibrium, a clear relationship between inhomogeneities in local entropy production and the degree to which active systems are out of equilibrium and capable to perform work has not been adequately established. The PI will explore how knowledge of spatial gradients in entropy production can be exploited to maximize the work active systems can perform at the microscale. The outcomes of this research will advance our current knowledge of statistical physics and will provide insight into how to design stimuli-responsive materials capable of performing work at the microscale. The numerical tools developed for this project should be transferable to other active systems and will have important implications for a number of biological problems that rely on similar physical mechanisms. The award contributes to the education of undergraduate and graduate students which the PI will recruit to participate in these projects, and they will have first-hand exposure to cutting-edge numerical and statistical methods to model active systems. Furthermore, an outreach plan in collaboration with a number of on-campus organizations such as WISC (Women in Science at Columbia), whose efforts are dedicated to the advancement of women and underrepresented minorities in the sciences, technology, engineering and math, is currently underway, and will be further 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.

该奖项支持理论研究和教育，旨在了解活性材料目前尚未探索的三个重要方面。活性物质是材料工程中一个令人兴奋的新领域，在过去的十年中得到了突出的发展。这是因为能够自我推进的微粒的发展。人们可以把这些粒子想象成细菌的合成类似物，它们的形状、表面化学和速度都可以在实验室里设计出来。在这个领域有几个基本问题需要解决，这为下一代智能材料的发展提供了新的机会。活性粒子形成的材料对外界刺激的弹性反应是什么？这是一个重要的问题，可以提高我们对从生物膜到上皮组织等大量材料的机械性能的理解。另一个未被探索的问题涉及到活动表面的行为。与合成囊泡不同，生物细胞的运动完全由复杂的生化反应决定。这使得它们的行为类似于主动系统。因此，了解表面/囊泡如何响应主动力是很重要的。例如，当成纤维细胞和上皮癌细胞被限制在刚性的、不对称的微通道中时，它们可以获得定向运动。PI将探索在多大程度上这种行为可以被一个更简单的系统捕获：一个装载活性粒子的合成囊泡。目标是开发能够模仿其机械行为的生物细胞的简单合成类似物。最后，主动系统的一个主要特征是它们打破了时间反转对称，即在粒子轨迹上向后运行时间确实会使粒子沿着它来的相同路径返回。这种情况在系统中发生的程度可以通过测量熵产来量化。该团队将测量一些活动系统的这一数量，并在熵产的空间梯度与活动系统失去平衡和能够工作的程度之间建立联系。这项研究的结果将为如何设计能够在微观尺度上执行工作的刺激反应材料提供见解。为该项目开发的数值工具应可转移到其他活动系统，并将对依赖类似物理机制的许多生物学问题产生重要影响。该奖项有助于PI将招募参与这些项目的本科生和研究生的教育，他们将有第一手的机会接触到最前沿的数值和统计方法来模拟活动系统。此外，与一些校园组织合作的外展计划，如WISC（哥伦比亚妇女科学），其努力致力于在科学，技术，工程和数学领域提高妇女和代表性不足的少数民族，目前正在进行中，并将进一步扩大。该奖项支持理论研究和教育，旨在理解活性材料目前尚未探索的三个重要问题。第一个问题涉及活性凝析油的流变性能。尽管大量的工作致力于研究活性胶体粒子的自组装、动力学和相行为，但在了解活性凝聚物的弹性特性及其对外部刺激的响应方面所做的工作有限。这是一个需要解决的基本问题，以便更好地表征这些材料的机械性能。第二个问题涉及使用允许拓扑转换的模型研究流体囊泡上的弹性力和主动力之间的相互作用。PI将探索当巨大的单层囊泡装载活性粒子时，在什么条件下可以发生整流。虽然已经做了大量的工作来理解单个活性粒子的运动纠正，但对于自推进粒子在微通道上激活的软的、可变形的界面的输运特性知之甚少。这是一个重要的问题，因为当成纤维细胞和上皮癌细胞被限制在不对称的周期性通道中时，它们可以获得定向运动，并将为描述这样一个复杂系统提供一个最小的模型。第三个问题是关于主动系统本质的一个基本问题。虽然在最基本的层面上，由于时间反转对称性破缺，出现了活动系统最有趣的现象学行为，而熵产生是缺乏平衡的标志，但局部熵产生的非均质性与活动系统脱离平衡和能够做功的程度之间的明确关系尚未充分建立。PI将探索如何利用熵产生的空间梯度知识来最大化主动系统在微观尺度上的工作。这项研究的结果将推进我们目前对统计物理学的了解，并将为如何设计能够在微观尺度上执行工作的刺激响应材料提供见解。为该项目开发的数值工具应可转移到其他活动系统，并将对依赖类似物理机制的许多生物学问题产生重要影响。该奖项有助于PI将招募参与这些项目的本科生和研究生的教育，他们将有第一手的机会接触到最前沿的数值和统计方法来模拟活动系统。此外，与一些校园组织合作的外展计划，如WISC（哥伦比亚妇女科学），其努力致力于在科学，技术，工程和数学领域提高妇女和代表性不足的少数民族，目前正在进行中，并将进一步扩大。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。