74th Annual Meeting of the APS Division of Fluid Dynamics (November 21, 2021 — November 23, 2021)

V0065: Self-propulsion of a Freely-Suspended, Rotationally-Symmetric Swimmer Enabled by Viscoelastic Normal Stresses

Authors

• Laurel A Kroo, Department of Mechanical Engineering, Stanford University
• Jeremy P Binagia, Department of Chemical Engineering, Stanford University
• Noah Eckman, Department of Chemical Engineering, Stanford University
• George Herring, Department of Electrical Engineering, Stanford University
• Manu Prakash, Department of Bioengineering, Stanford University
• Eric S G Shaqfeh, Department of Mechanical Engineering and Department of Chemical Engineering, Stanford University

DOI: https://doi.org/10.1103/APS.DFD.2021.GFM.V0065

Here we present a physical implementation of an untethered robot capable of propulsion at low Reynolds number -- only when submerged in a non-Newtonian fluid. This optically controlled, battery-powered robot propels itself in the direction of  the larger “head”.  By controlling the relative rotation rate while recording motility, we propose a novel application of this robot to function as a rheological probe of its local surrounding fluid. This proof-of-concept device experimentally demonstrates that a unique propulsion mechanism exists for elastic, non-Newtonian fluids.