发表机构
Tufts University; Institute for Mechanobiology, Department of Bioengineering, College of Engineering, Northeastern University; Department of Mechanical Science and Engineering, University of Illinois Urbana-Champaign; Department of Mechanical Engineering and Applied Mechanics, University of Pennsylvania（塔夫茨大学; 东北大学生物工程学院机制生物学研究所; 伊利诺伊大学厄巴纳-香槟分校机械科学与工程系; 宾夕法尼亚大学机械工程和应用力学系）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本研究通过直接拉格朗日追踪单个DNA分子，揭示黏弹性流中聚合物构象动力学，发现经典本构模型无法完全捕捉瞬态动力学，强调需考虑聚合物分子内力学以改进黏弹性流的本构描述。
AI 中文摘要
黏弹性流体的复杂流动行为源于流体应力与其组成聚合物链非平衡构象动力学之间的反馈作用。尽管本构模型可预测简单几何结构中的流动与应力场，但对具有混合运动学和非平凡聚合物动力学的黏弹性流的调控机制，仍缺乏基础理解。量化流动中聚合物链依赖于历史的构象，是解决这些复杂系统的关键。为填补这一知识空白，我们采用单个DNA分子的直接拉格朗日追踪，揭示其在微流控黏弹性流中的构象动力学，研究不同聚合物轮廓长度和浓度的情况。对比测得的分子伸展与取向，发现其与经典本构模型存在差异，经典模型无法完全捕捉瞬态动力学。我们的测量结果显示，聚合物的弛豫和形状存在明显各向异性，该各向异性通过流体阻力耦合聚合物的旋转与伸展，调控其拉格朗日力学。这些发现强调了聚合物拉格朗日历史的重要性，以及需考虑非平凡分子内力学，以改进黏弹性流的本构描述。
英文摘要
The complex flow behavior of viscoelastic fluids emerges from a feedback between fluid stress and the out-of-equilibrium conformational dynamics of their constituent polymer chains. While constitutive models can predict flow and stress fields in simple geometries, a fundamental understanding of the mechanisms regulating viscoelastic flows with mixed kinematics and non-trivial polymer dynamics remains elusive. Quantifying the history-dependent conformation of polymer chains in flow is essential to resolve these complex systems. To address this knowledge gap, we employ direct Lagrangian tracking of individual DNA molecules to reveal their conformational dynamics in microfluidic viscoelastic flows for different polymer contour lengths and concentrations. Comparing the measured molecular extension and orientation reveals discrepancies with canonical constitutive models, which do not fully capture the transient dynamics. Our measurements show a distinct anisotropy in polymer relaxation and shape, which couple the polymer's rotation and extension through hydrodynamic drag, regulating their Lagrangian mechanics. These findings emphasize the importance of Lagrangian polymer history and the need to account for non-trivial intra-molecular mechanics to improve constitutive descriptions of viscoelastic flows.
