Shear-induced chiral migration of particles with anisotropic rigidity.

We report that an achiral particle with anisotropic rigidity can migrate in the vorticity direction in shear flow. A minimal "tetrumbbell" model of such a particle is constructed from four beads and six springs to make a tetrahedral structure. A combination of two different spring constants corresponding to "hard" and "soft" springs yields ten distinguishable tetrumbbells, which when simulated in shear flow with hydrodynamic interactions between beads but no Brownian motion at zero Reynolds number, produces five different types of behavior in which seven out of ten tetrumbbell structures migrate in the vorticity direction due to shear-induced chirality. Some of the structures migrate in the same direction along the vorticity direction even when the shear flow is reversed, which is impossible for permanently chiral objects.