Bubble size control and measurement in the generation of ferrofluid foams

Ordered ferrofluid foams in tubes or channels offer promising possibilities for transporting and processing small gas (or liquid) samples. For this purpose, monodisperse bubbles can be produced, with fine control of their volume over at least three orders of magnitude, by the application of a variable magnetic field gradient during bubble generation. Electrical resistance measurements can be used to count bubbles, determine their volume, and identify the foam structure they form in the tube or channel. (C) 2003 American Institute of Physics.