1. NTNU Nanomechanical Lab, Department of Structural Engineering, Norwegian University of Science and Technology (NTNU), 7491 Trondheim, Norway
2. Catalan Institute of Nanoscience and Nanotechnology (ICN2), (ICN-CSIC) Barcelona, Campus UAB, E08193 Bellaterra, Spain
3. ICREA—Institució Catalana de Recerca i Estudis Avançats, 08010 Barcelona, Spain