1. Department of Applied Science and Technology, Politecnico di Torino, Corso Duca degli Abruzzi 24, 10129 Torino, Italy
2. Department of Physics, University of Torino, Via Pietro Giuria 1, 10125 Torino, Italy
3. Laboratory of Bio-Inspired and Graphene Nanomechanics, Department of Civil, Environmental and Mechanical Engineering, University of Trento, Via Mesiano 77, 38123 Trento, Italy
4. Center for Materials and Microsystems, Fondazione Bruno Kessler, Via Sommarive 18, 38123 Povo (Trento), Italy
5. School of Engineering and Materials Science, Queen Mary University of London, Mile End Road, London E1 4NS, United Kingdom