Detachment of particles and particle clusters from liquid/liquid interfaces

The detachment of microspheres from a liquid/liquid interface triggered by body forces is studied experimentally, both for the case of single particles and for particle clusters. The values of the critical force required to detach particles from the interface are in agreement with the maximum values of the wetting force keeping a particles at the interface. In the case of particle clusters, a rearrangement of the cluster configuration from a raft to a more compact structure is observed when the body force is increased. Clusters detach from the liquid/liquid interface at smaller acceleration values than single particles. The critical accelerations required to detach particle clusters are consistent with models assuming that the wetting force acts at the circumference of a spherical or hemispherical densely packed particle cluster. These models predict that the critical acceleration for particle clusters scales as n(-2/3), where n is the number of particles in a cluster.