Hydrodynamically induced jamming in colloidal particles flow-driven across a potential landscape

We will show that when several colloidal particles are driven by the flow of the medium, hydrodynamic interactions can hinder their collective transport across potential barriers. This result contrasts with previous reports of force-driven systems, where hydrodynamic interactions facilitate particle motion. Experimentally, we observe this phenomenon by driving colloidal particles using rotating optical traps, which creates a vortex flow field in the corotating reference frame. This produces a jamming-like decrease of the current as density is increased, which can also be seen in simulations. A minimal theoretical model shows that hydrodynamic interactions between particles enhance the external potential, and this causes the average velocity reduction. The impact of hydrodynamic interactions is reversed compared to force-driven motion, suggesting that our findings are a generic feature of flow-driven transport.