1. Department of Engineering Mechanics, KTH Royal Institute of Technology, Stockholm SE-10044, Sweden
2. Wallenberg Wood Science Center, KTH Royal Institute of Technology, Stockholm SE-10044, Sweden
3. Pritzker School of Molecular Engineering, University of Chicago, Chicago, Illinois 60637, United States
4. Department of Fibre and Polymer Technology, KTH Royal Institute of Technology, Stockholm SE-10044, Sweden