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

这笔拨款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--类似于自然肌肉如何收缩和伸长以产生运动和力量。大多数软生物材料依赖于机械功从纳米级分子马达到宏观尺度的有效转移。这是由复杂和架构完善的内部网络确保的。这个网络由分子机器组成，它们协同地“拉”聚合物的“绳索”。这一行动是一场推动经济收缩的微观拉锯战。这个项目将重点放在通过结合人工分子机器(轮烷)来复制这种机制。为此，该项目将开发一个多尺度模型，并辅之以实验，可以连接活性分子机制和宏观反应。这项研究的结果将使活性材料/机器的创造具有无数的生物力学应用。它还将促进合作，并激励力学和材料科学边缘的新一代研究人员。计划的活动包括面向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。研究的具体目标是了解滑动环凝胶中的分子机制、分子马达中的能量输入和宏观凝胶的紧急收缩之间的关系。为此，该研究项目将把理论/计算力学、化学合成和机械表征整合在一个反馈回路中，在这个回路中，模型和实验将相互学习。该模型以统计力学为基础，将提供分子过程(环滑动、环坍塌、…)之间的明确联系以及宏观的流变性、弹性和收缩。反过来，实验将由该模型指导，从而实现合理的设计。该项目的具体目标是(A)开发一个各向同性拓扑凝胶的模型，以连接分子结构和力学响应，(B)使用该模型来探索各向异性滑环/纤维素网络的机制，以及(C)调查和确定在收缩过程中放大跨尺度的力传递的条件。通过这些目标，该项目将推动滑环网络的内部工作原理被用作分子机器，并使能够像自然肌肉一样收缩的仿生材料的合理开发。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。

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.