Controlling trajectories via particle shape in confined flows

Transport properties of particles in confining geometries show very specific characteristics, as for example lateral drift for fibers inclined with respect to the flow direction. Due to viscous friction with top and bottom walls particles act like moving obstacles and induce strong flow perturbations. These perturbations are at the origin of the observed lateral drift, oscillatory movement between lateral walls or the deformation of flexible fibers. Modifying the fiber shape by adding for example an additional arm leads to an L shaped fiber and thus breaks the previous fiber symmetry. This induces fiber rotation until a stable equilibrium orientation is reached. Lateral drift is then observed until interaction with side walls becomes important. Tuning the fiber asymmetry and confinement allows for a precise control of particle trajectories, including the approach of side walls, even robust against small perturbations. Our investigation combines precise microfluidic experiments as well as numerical simulations based on modified Brinkman equations. The knowledge gained here can be used for targeted delivery or particle capture inside microchannels.