Can we predict the death of a granular raft?

Driven by capillary attraction, non-Brownian particles straddling at an interface between two immiscible fluids self-assemble into a closed-packed monolayer called granular rafts. When such rafts are subjected to compression, they usually behave as elastic solids forming wrinkles and eventually fail by buckling of the interface. In certain instances, instead of a system-scale buckling, individual particles are ejected from the interface. In our talk we investigate this dual nature of rafts in light of the individual particle stability and dynamics. We observe that by modifying the size, surface wettability of particles or the densities, interfacial tension of the fluids, we not only change the particle stability at the interface but also the raft failure mode. We hypothesize that if the energy to buckle a raft is more than the energy required to remove a particle from the interface, the raft would fail via ejection of particles. As the energy to remove a particle can be modified not only with the particle's static equilibrium position but also with the dynamics of the three-phase contact line, we also test if a change in raft failure mode can be achieved just by roughening the individual particles in a raft.