Department of Physics and Biophysics, University of San Diego, San Diego, CA, 92110, USA.
Nat Commun. 2022 Sep 2;13(1):5180. doi: 10.1038/s41467-022-32876-y.
How local stresses propagate through polymeric fluids, and, more generally, how macromolecular dynamics give rise to viscoelasticity are open questions vital to wide-ranging scientific and industrial fields. Here, to unambiguously connect polymer dynamics to force response, and map the deformation fields that arise in macromolecular materials, we present Optical-Tweezers-integrating-Differential -Dynamic-Microscopy (OpTiDMM) that simultaneously imposes local strains, measures resistive forces, and analyzes the motion of the surrounding polymers. Our measurements with blends of ring and linear polymers (DNA) and their composites with stiff polymers (microtubules) uncover an unexpected resonant response, in which strain alignment, superdiffusivity, and elasticity are maximized when the strain rate is comparable to the entanglement rate. Microtubules suppress this resonance, while substantially increasing elastic storage, due to varying degrees to which the polymers buildup, stretch and flow along the strain path, and configurationally relax induced stress. More broadly, the rich multi-scale coupling of mechanics and dynamics afforded by OpTiDDM, empowers its interdisciplinary use to elucidate non-trivial phenomena that sculpt stress propagation dynamics-critical to commercial applications and cell mechanics alike.
局部应力如何在聚合物流体中传播，更一般地说，大分子动力学如何导致粘弹性，这些都是对广泛的科学和工业领域至关重要的开放性问题。在这里，为了明确将聚合物动力学与力响应联系起来，并绘制出在高分子材料中出现的变形场，我们提出了光学镊子集成微分动态显微镜（OpTiDMM），它可以同时施加局部应变、测量阻力并分析周围聚合物的运动。我们用环形和线性聚合物（DNA）的混合物及其与刚性聚合物（微管）的复合材料进行的测量揭示了一种意想不到的共振响应，当应变率与缠结率相当时，应变对齐、超扩散和弹性达到最大值。微管抑制了这种共振，同时由于聚合物在应变路径上的堆积、拉伸和流动以及构象松弛引起的应力的程度不同，大大增加了弹性储存。更广泛地说，OpTiDDM 提供的力学和动力学的丰富多尺度耦合，使其能够跨学科使用，以阐明塑造应力传播动力学的非平凡现象——这对商业应用和细胞力学都至关重要。
