1. Applied Stem Cell Technologies Technical Medical Centre University of Twente PO Box 217 Enschede 7500 AE The Netherlands
2. BIOS Lab on a Chip group Technical Medical Centre MESA+ Institute for Nanotechnology University of Twente PO Box 217 Enschede 7500 AE The Netherlands
3. National Centre for Nano Fabrication and Characterization DTU Nanolab Technical University of Denmark Kgs. Lyngby 2800 Denmark
4. Department of Anatomy and Embryology Leiden University Medical Center Leiden 2300 RC The Netherlands