The problem posed by Unilever concerns the formation and transport of droplets in an interconnected network of microchannels. Two streams, one of oil and one of water, feed into the device network and interact, producing oil droplets of a controlled size as the output. For manufacturing processes, Unilever wishes to parallelize massively a process such as droplet formation with a large number of output channels producing droplets of equal size. However, their experiments reveal that instabilities in the flow pattern lead to some output channels containing single-phase flow or at least inconsistent droplet formation. Unilever would like to understand what network design features lead to such behaviour. A further related question is how to make such a network robust, in order that fouling and blocking of one part of the system will not have catastrophic consequences on the entire manufacturing process.

Problem presented by
John Melrose and Guoping Lian, Unilever Corporate Research

Study Group contributors
John Billingham (University of Nottingham)
Andrew Grief (University of Oxford)
John Hinch (University of Cambridge)
David Leppinen (University of Cambridge)
Shailesh Naire (Heriot-Watt University)
John Ockendon (University of Oxford)
Nick Ovenden (University College London)
Howell Peregrine (University of Bristol)
Colin Please (University of Southampton)
Jean-Marc Vanden-Broeck (University of East Anglia)
Gorden White (University of Oxford)
Eddie Wilson (University of Bristol)

Further reading
Microfluidics begins to make its mark, Global Watch magazine (Feb 2006)