A variety of useful materials and structures can be engineered by binding microscopic solid particles to liquid interfaces. But the dynamics of binding and the interactions that control it are still not well understood.Using digital holographic microscopy, a fast 3D imaging technique, we measure the motion of colloidal particles near a liquid interface. We find that micrometer-sized polymer particles take a surprisingly long time -- weeks or even months -- to bind and relax to equilibrium. This behavior can be understood in terms of contact-line pinning. I will discuss how the pinning might affect the self-assembly of such particles after they bind.
