1. Department of Physics and Earth Science, University of Ferrara, I-44122 Ferrara, Italy
2. Istituto Nazionale di Fisica Nucleare, Ferrara Division, I-44122 Ferrara, Italy
3. INRIM, Advanced Materials and Life Sciences Division, Str. delle Cacce, 91, I-10135 Torino, Italy
4. BIOtech Research Center, Department of Industrial Engineering, University of Trento, I-38123, Trento, Italy
5. Laboratory for Bioinspired, Bionic, Nano, Meta, Materials & Mechanics, Department of Civil, Environmental and Mechanical Engineering, University of Trento, I-38123 Trento, Italy
6. Department of Animal Biosciences, Swedish University of Agricultural Sciences, 750 07 Uppsala, Sweden
7. School of Engineering and Materials Science, Queen Mary University of London, Mile End Road, London E1 4NS, U.K.