1. Laboratory for Micro and Nanotechnology, Paul Scherrer Institute, 5232 Villigen, Switzerland
2. Swiss Nanoscience Institute, University of Basel, 4056 Basel, Switzerland
3. Laboratory of Nanoscale Biology, Paul Scherrer Institute, 5232 Villigen, Switzerland
4. Laboratory of Biomolecular Research, Paul Scherrer Institute, 5232 Villigen, Switzerland