This article is part of the Microfluidics web themed issue Guest editors: Andrew deMello, Florian Hollfelder and Klavs Jensen All articles in this issue will be gathered together online at www.rsc.org/microfluidics Published on 21 December 2012. Downloaded by Universitat des Saarlandes on 27/11/2014 16:31:29. View Article Online View Journal | View Issue