1. Mesoscale Chemical Systems Group, MESA+ Research Institute, University of Twente, ME147, P.O. Box 217, 7500AE Enschede, The Netherlands
2. Physics of Fluids Group, MIRA and MESA+ Research Institutes, Faculty of Science and Technology, University of Twente, P.O. Box 217, 7500AE Enschede, The Netherlands
3. Department of Cario-, Endo- and Periodontology, Academic Center for Dentistry, Amsterdam, The Netherlands