1. Departament of Applied Physics, EEI, Universitat Politècnica de Catalunya, Pça
Rei 15, Igualada 08700, Spain
2. Department of Materials, Institute of Polymers, Swiss Federal Institute of Technology, ETH Zurich, Wolfgang-Pauli-Str.
10, 8093 Zurich, Switzerland
3. Departament of Chemical Engineering, ETSEIB, Universitat Politècnica de Catalunya, Diagonal 647, Barcelona
E-08028, Spain
4. Centre for
Research in Nano-Engineering, Universitat Politècnica de Catalunya, Edifici C′, C/Pasqual i Vila s/n,
Barcelona E-08028, Spain