Magnetically responsive pickering foams.

We introduce a new class of Pickering foams which can be manipulated using a magnetic field. These foams are stabilized by a mixture of magnetic and nonmagnetic particles. They exhibit excellent stability in the absence of a magnetic field, but can be rapidly destroyed on demand with the application of a threshold field. We characterize their stability in the absence of a magnetic field by measuring the rate of water drainage from the foam as a function of time. We also correlate their collapse behavior under a magnetic field to the foam liquid fraction, as well as the concentration of magnetic particles in the foam. This novel system can be used to study the properties of Pickering foams, and has potential applications in noncontact defoaming processes.