Measuring the Translation-Rotation Coupling of an Isotropic Helicoid

In 1871, Lord Kelvin proposed the isotropic helicoid, a chiral particle whose translation-rotation coupling is independent of orientation. Recent experiments have not been able to observe the expected chiral coupling, while new theory has shown that hydrodynamic interactions between the vanes of an isotropic should allow a nonzero but small translation-rotation coupling. We are performing the next generation of experiments in search of this nonzero-coupling. The effort involves two experiments. In the first experiment, we suspend the test particle and measure torque generated by fluid flowing past it. In the second experiment, we measure the rotation of a sedimenting particle in a quiescent fluid.