Mechanics of Active Slide-Ring Networks: from Molecular Motors to Molecular Machine

这项资助将侧重于了解新型聚合物的分子结构如何影响它们的收缩能力——类似于天然肌肉如何收缩和延长以产生运动和力量。大多数软质生物材料依赖于从纳米级分子马达到宏观尺度的机械功的有效传递。这是由一个复杂和架构的内部网络来保证的。该网络由分子机器组成，这些分子机器协同“拉”聚合物“绳”。这是一场推动收缩的微观拔河。本项目将着重于通过结合人工分子机器（轮烷）来复制这些机制。为此，该项目将开发一个多尺度模型，辅以实验，可以连接活性分子机制和宏观反应。这项研究的成果将使具有无数生物力学应用的活性材料/机器的创造成为可能。它还将促进合作，激励力学和材料科学前沿的新一代研究人员。计划的活动包括针对高中生和本科生的主动学习模块，这些学生参与研究，以及在社交媒体上传播研究成果。该研究的具体目标是了解滑动环凝胶的分子机制、分子马达的能量输入和宏观凝胶的紧急收缩之间的关系。为此，该研究项目将在一个反馈回路中整合理论/计算力学、化学合成和力学表征，其中模型和实验将相互学习。该模型基于统计力学，将提供分子过程（环滑动、环坍塌等）与宏观流变、弹性和收缩之间的清晰联系。反过来，实验将以模型为指导，从而实现合理的设计。该项目的具体目标是：(a)开发各向同性拓扑凝胶模型，以连接分子结构和机械响应，(b)使用该模型探索各向异性滑环/纤维素网络的力学，以及(c)调查和确定在收缩过程中放大跨尺度力传递的条件。通过这些目标，该项目将推进滑动环网络的内部工作，将其用作分子机器，并使能够像天然肌肉一样收缩的仿生材料得到合理开发。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。

This grant will focus on understanding how the molecular structure of novel polymers affects their ability to contract - similar to how natural muscles contract and lengthen to generate motion and force. Most soft biological materials rely on the efficient transfer of mechanical work from nanoscopic molecular motors to the macroscale. This is ensured by a sophisticated and architected internal network. That network consists of molecular machines that cooperatively “pull” on polymer “ropes”. This action is a microscopic tug-of-war that drives contraction. This project will focus on the replication of such mechanisms by combining artificial molecular machines (rotaxanes). For this, the project will develop a multiscale model, complemented by experiments, that can bridge active molecular mechanisms and the macroscopic response. Outcomes of this research will enable the creation of active materials/machines with a myriad of biomechanical applications. It will also promote collaborations and inspire a new generation of researchers at the edge of mechanics and materials science. Planned activities include active learning modules for high-school and undergraduate students, the involvement of these students in research, and the dissemination of research findings in social media.The specific goal of the research is to understand the relationship between molecular mechanisms in slide-ring gels, the energy input in molecular motors, and the emergent contraction of the macroscopic gel. For this, the research project will integrate theoretical/computational mechanics, chemical synthesis, and mechanical characterization in a feed-back loop, where model and experiments will learn from one-another. The model, based on statistical mechanics, will provide a clear connection between molecular processes (ring sliding, ring collapse, …) and the macroscopic rheology, elasticity, and contraction. In turn, experiments will be guided by the model so that a rational design can be achieved. The objectives of the project are specifically to (a) develop a model for isotropic topological gels to connect molecular architecture and mechanical response, (b) use this model to explore the mechanics of anisotropic slide-ring/cellulose networks, and (c) investigate and identify conditions that amplify the force transfer across scales during contraction. Through these aims, the project will advance the inner workings of slide ring networks to be used as molecular machines and enable the rational development of a biomimetic material capable of contracting as does natural muscle.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.