Competition of velocities in the failure of particle rafts under tension

Particle rafts are two-dimensional single-layers of aggregated sub-millimeter polydisperse particles floating at an air-liquid interface. The failure of such rafts under tension shows distinct morphologies that depend on the pulling velocity, V_pull. At high V_pull, numerous small cracks are distributed diffusely throughout the entire system; as V_pull decreases, the distance between adjacent cracks increases; at low V_pull, the raft disconnects into two pieces in a necking event that resembles ductile failure. We model this behavior as a particle chain with inter-particle adhesion provided by lateral capillary forces. As the chain is pulled apart, this model predicts a wave-vector-dependent healing velocity, V_heal(k), for the particles to rearrange and rebond with one another.  V_heal(k) competes with the applied V_pull to produce features that are consistent with our experimental measurements.