Juggling with bubbles in cylindrical ferrofluid foams

Monodisperse foams in long cylinders exhibit ordered spiral structures. We have made ferrofluid foams of this kind and find that they can be manipulated in a variety of ways by an external magnetic field. Effects include morphological changes, twisting of structures and size control in the bubble formation process. This offers a promising technique for the efficient transport, switching and combining of samples in fluidic networks, possibly on the microfluidic scale.