Ralf Eichhorn
Nordita, Stockholm, Sweden

Separation of chiral colloidal particles in micro-flows

We study the motion of chiral colloidal particles in microfluidic devices. Using computer simulations and analytical arguments, we reveal that the particles migrate with chirality-specific average velocities through a microfluidic channel, provided the driving flow breaks the mirror symmetry. Experimentally, we exploit this effect to separate micron-sized chiral particles in a helical fluid flow which is created inside a microfluidic device patterned with slanted grooves. The experimental results are confirmed by numerical calculations, which demonstrate how the coupling of rotational and translational degrees of freedom leads to differences in the trajectories of particles with opposite chirality. Such an effect may be of practical relevance for the separation of chiral molecules.