1. Laboratory of Microsystems LMIS4, Ecole Polytechnique Fédérale de Lausanne, Lausanne 1015, Switzerland
2. Laboratory of Bio- and Nano- Instrumentation, Ecole Polytechnique Fédérale de Lausanne, Lausanne 1015, Switzerland
3. Laboratory of Cellular Optics II, Department of Physiology, University of Bern, Bern 3012, Switzerland