Work

Lagrangian dynamics unveil polymer conformation in viscoelastic flows

Year: 2026

Type: preprint

Abstract: 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.

Source: arXiv (Cornell University)

DOI: 10.48550/arxiv.2609.04538

Authors: Thorens, Louison, Juarez, Gabriel, Guasto, Jeffrey S., Arratia, Paulo E.

Institutions: Tufts University, Northeastern University, University of Illinois Urbana-Champaign, University of Pennsylvania

Language: English

Topic: Rheology and Fluid Dynamics Studies

Subfield: Fluid Flow and Transfer Processes

Field: Chemical Engineering

Domain: Physical Sciences

Open Access status: green

Funders: National Science Foundation, Gordon and Betty Moore Foundation, Division of Chemical, Bioengineering, Environmental, and Transport Systems, Division of Civil, Mechanical and Manufacturing Innovation

Awards: Lagrangian Transport in Active Matter Flows, Collaborative Research: Elucidating the Diversity of Bacterial Flagellation and Motility Through Mechanics, G5363092874, The Effects of Viscoelasticity on Filament Thinning & Drop Breakup in Microfluidic Devices: Single Molecule Experiments, Collaborative Research: Stability and dispersion of viscoelastic flows through porous media, Collaborative Research: CBET-EPSRC: Investigation of Coherent Structures in Elastic and Elasto-inertial Turbulence

OpenAlex ID: W7211908136

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Cited by: 1

Related to: 10