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Active turbulence in shear-thinning fluid

Hongyi Bian1, Chunhe Li1, Zixiang Lin1, Jin Zhu1, Weijie Chen2, Gaojin Li3, Yongxiang Huang4, and Zijie Qu1,*

  • 1Global College, Shanghai Jiao Tong University, Shanghai 200240, People's Republic of China
  • 2Intelligent Medicine Institute, Shanghai Medical College, Fudan University, Shanghai 200032, People's Republic of China
  • 3State Key Laboratory of Ocean Engineering, School of Ocean & Civil Engineering, Shanghai Jiao Tong University, Shanghai 200240, People's Republic of China
  • 4State Key Laboratory of Marine Environmental Science & Center for Marine Meteorology and Climate Change & College of Ocean and Earth Sciences, Xiamen University, Xiamen 361102, People's Republic of China

  • *Contact author: zijie.qu@sjtu.edu.cn
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Phys. Rev. Research 8, 013318 – Published 25 March, 2026

DOI: https://doi.org/10.1103/z22f-3v22

Abstract

The study of active matter system has critical importance in revealing the physical essence of biological collective behavior. Dense bacterial suspension—a typical biological active matter, exhibits a wide range of phenomenona, among which bacterial turbulence has received extensive interest in recent years. This seemingly chaotic motion is widely studied in Newtonian fluid. However, studies based on complex fluids have predominantly focused on viscoelastic effects, leaving the role of shear-thinning viscosity largely unexplored despite its prevalence in natural bacterial environments like mucus and gastric fluids. Here, we experimentally employed Ficoll and Methocel polymers to study the impacts of various viscosities by Newtonian fluid and shear-thinning effects by non-Newtonian fluids on bacterial turbulence. We analyzed various physical properties, including energy, enstrophy, etc., and observed that the shear-thinning effect is significantly suppressed in high-concentration bacterial suspensions. While the ordered arrangement of polymer chains under shear flow leads to the microscopic anisotropic viscosity, the suppression is largely attributed to the disruption of polymer chains caused by strong interbacterial interactions in dense suspensions. To validate this hypothesis, we conducted experiments at a lower bacterial concentration and verified the findings using theoretical calculations based on the modified resistive force theory.

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Phys. Rev. Research 8, 013318– Published 25 March, 2026
  • Received 31 July 2025
  • Accepted 19 February 2026
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Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.

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