Modeling the relative dynamics of DNA-coated colloids

A versatile way to makes colloids with programmable interactions is to coat them with strands of sticky DNA. However, the DNA changes the dynamics of the colloids, in ways that can push the system out of equilibrium on experimental timescales. We construct a coarse-grained theoretical model for the relative dynamics of DNA-coated colloids (which is similar to models of molecular motors), and use it to argue that (a) DNA induces friction between the points of contact that can be about 100 times larger than hydrodynamic friction, for relevant experimental parameters, and (b) the friction for particles rolling could be several orders of magnitude smaller than the friction for sliding, when the DNA is very short and stiff. Therefore, we speculate that in certain experimental systems such colloids could act like gears, and assemble into metastable states that would not be observed in their true equilibrium.