Micropropulsion and microrheology in complex fluids via symmetry breaking

ORAL

Abstract

Many biological fluids have polymeric microstructures and display non-Newtonian rheology. We take advantage of such nonlinear fluid behavior and combine it with geometrical symmetry-breaking to design a novel small-scale propeller able to move only in complex fluids. Its propulsion characteristics are explored numerically in an Oldroyd-B fluid for finite Deborah numbers while the small Deborah number limit is investigated analytically using a second-order fluid model. We then derive expressions relating the propulsion speed to the rheological properties of the complex fluid, allowing thus to infer the normal stress coefficients in the fluid from the locomotion of the propeller. Our simple mechanism can therefore be used either as a non-Newtonian micro-propeller or as a micro-rheometer.

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Authors

  • On Shun Pak

    Department of Mechanical and Aerospace Engineering, University of California San Diego

  • Lailai Zhu

    KTH Mechanics, KTH Mechanics, Linne flow centre, Royal Institute of technology, Sweden, KTH Mechanics, Royal Institute of technology

  • Luca Brandt

    KTH Mechanics, KTH Mechanics, Linne flow centre, Royal Institute of technology, Linne' Flow Centre, KTH Mechanics - 10044, Stockholm - Sweden, KTH Mechanics, Royal Institute of technology, KTH, Stockholm

  • Eric Lauga

    Department of Mechanical and Aerospace Engineering, University of California, San Diego, Department of Mechanical and Aerospace Engineering, University of California San Diego, Department of Mechanical and Aerospace Engineering, UC San Diego, University of California San Diego, University of California at San Diego, University of California, San Diego