Lord Kelvin's isotropic helicoid

Nearly 150 years ago, Lord Kelvin proposed the isotropic helicoid, a particle with isotropic yet chiral interactions with a fluid so that translation couples to rotation. An implementation of his design fabricated with a three-dimensional printer is found experimentally to have no detectable translation-rotation coupling, although the particle point-group symmetry allows this coupling. We explain these results by demonstrating that in Stokes flow, the chiral coupling of such isotropic helicoids made out of nonchiral vanes is due only to hydrodynamic interactions between these vanes. Therefore it is small. In summary, Kelvin's predicted isotropic helicoid exists, but only as a weak breaking of a symmetry of noninteracting vanes in Stokes flow.

Automated summary

The isotropic helicoid proposed by Lord Kelvin nearly 150 years ago has been experimentally confirmed to exist, with its chiral coupling attributed to hydrodynamic interactions between the nonchiral vanes. This coupling effect is small due to the nature of the interactions.