Helical Ribbons: Simple Chiral Sedimentation

Abstract

We investigate the sedimentation of chiral particles in viscous fluid flow. We identify helical ribbons as simple particles with strong translation-rotation coupling whose symmetry ensures that the centers of mass, buoyancy, resistance, and mobility coincide. Experimental measurements of both relevant mobility tensors show excellent agreement with simulations of ribbons made of interacting spheres. We observe quasi-periodic angular dynamics causing complex spatial trajectories. In tilt-spin phase space, orbits are closed due to time-reversal and reflection symmetry. Changing the helical ribbon length reveals a bifurcation at which the stable sedimentation orientations switch.

7 pages, 6 figures

References in corpus (4)

• Spinning and tumbling of long fibers in isotropic turbulence
• Angular dynamics of small crystals in viscous flow
• U-shaped disks in Stokes flow: Chiral sedimentation of a non-chiral particle
• Microscopic motility of isolated E. coli flagella

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