  Understanding multibody interactions between colloidal particles out of
equilibrium has a profound impact on dynamical processes such as colloidal self
assembly. However, traditional colloidal interactions are effectively
quasi-static on colloidal timescales and cannot be modulated out of
equilibrium. A mechanism to dynamically tune the interactions during colloidal
contacts can provide new avenues for self assembly and material design. In this
work, we develop a framework based on polymer-coated colloids and demonstrate
that in-plane surface mobility and mechanical relaxation of polymers at
colloidal contact interfaces enable an effective, dynamic interaction.
Combining analytical theory, simulations, and optical tweezer experiments, we
demonstrate precise control of dynamic pair interactions over a range of
pico-Newton forces and seconds timescales. Our model may be used to engineer
colloids with exquisite control over the kinetics and thermodynamics of
colloidal self-assembly dynamics via interface modulation and nonequilibrium
processing.
