Control of Molecular Fiber Bundle Mechanics and Dynamics by Bundle Architecture

生物纤维束在自然界中广泛存在。它们对我们的听觉和平衡感、促进伤口愈合、使细胞分裂和迁移都是必需的，这只是举几个例子。大自然利用纤维束的快速组装和拆卸，并通过分子相互作用的变化快速控制机械性能。了解生物纤维束及其丰富的力学和动力学特性对生物力学和机械生物学至关重要。然而，由于缺乏合适的微观技术来同时观察束的结构和动力学，这种理解受到了阻碍。该研究通过结合高精度位置测量、光响应测量和对自然界中广泛使用的原型光纤束结构的操作来解决这一问题。本研究的总体目标是确定生物纤维束的分子结构与其宏观力学性能之间的联系。这种理解对于生物医学研究和设计自组装和表现出可预测特性的新型智能材料至关重要。学生将接触到丰富的跨学科环境，包括理论物理，物理化学，分子生物学和材料科学，从而培养他们发展跨学科的研究方法。学生将参与国际合作，发展最先进的仪器将提高研究的有意竞争力。作为《爱丽丝梦游仙境》外展项目的一部分，女高中生也将参与这项研究。该项目将促进我们对生物纤维束结构与宏观力学和动力学之间联系的基本理解。这一发现可能在其他生物纤维束系统和人造系统中具有广泛的应用前景。微管将被用作模型系统。这些特殊的纤维束由平行的原丝组成，原丝排列成封闭的管状和其他束状结构。它们是束力学和动力学综合研究的理想材料，因为原丝之间的弱相互作用使它们很容易适应各种结构。采用新颖的高带宽位置检测方案，利用微管自然产生的热形状波动来测量微管的力学和动力学特性。结构将由光散射信号确定。实验验证了一个假设，即束的力学和动力学可以用最近发展起来的虫状束模型来描述，该模型的参数范围很广，如丝数、交联强度和亚基的分子状态。虫状纤维束模型提供了分子和宏观特性之间的直接联系，如果得到证实，将有助于智能纤维束材料的合理设计和组装，用于技术应用和生物医学研究。

Biological fiber bundles are widely spread in nature. They are necessary for our senses of hearing and balance, facilitate wound healing, and enable cells to divide and migrate, to name just a few examples. Nature utilizes fiber bundles for their fast assembly and disassembly and rapid control over mechanical properties through changes in molecular interactions. The understanding of biological fiber bundles and their rich mechanical and dynamical properties is crucial to biomechanics and mechanical biology. This understanding, however, has been hampered by a lack of suitable microscopic techniques for simultaneously observing bundle architecture and dynamics. The research addresses this problem by combining high-precision position measurements, optical response measurements and manipulation of a prototype fiber bundle structure that is widely used in nature. The overall goal of this research is to determine the link between the molecular architecture of biological fiber bundles and their macroscopic mechanical properties. This understanding is essential for biomedical research and for the design of novel smart materials that self-assemble and exhibit predictable properties. Students will be exposed to a rich interdisciplinary environment that includes theoretical physics, physical chemistry, molecular biology and material science, thereby training them to develop an interdisciplinary approach towards research. Students will participate in an international collaboration, and the development of state of the art instrumentation will enhance the intentional competitiveness of the research. Female high school students will also participate in the research as part of the Alice in Wonderland outreach project.The project will advance our fundamental understanding of the link between biological fiber bundle architecture and macroscopic mechanics and dynamics. The findings could potentially have wide spread applications to other biological fiber bundle systems and manmade systems. Microtubules will be used as a model system. These particular fiber bundles consist of parallel protofilaments that arrange themselves to form closed tubes and other bundle structures. They are ideal for comprehensive study of bundle mechanics and dynamics because the weak interactions between protofilaments allow them to easily adapt various structures. The mechanical and dynamical properties or microtubules will be measured using their naturally occurring thermal shape fluctuations with a novel high-bandwidth position detection scheme. The architecture will be determined from optical scattering signals. The experiments test the hypothesis that bundle mechanics and dynamics can be described by the recently developed wormlike bundle model over a wide range of parameters such as filament number, strength of crosslinking, and the molecular state of the subunits. The wormlike bundle model provides a direct link between molecular and macroscopic properties and, if confirmed, will aid the rational design and assembly of smart fiber bundle-based materials for technical applications and biomedical research.