1. Department of Materials, ETH Zurich, Vladimir-Prelog-Weg 5, 8093 Zurich, Switzerland
2. Laboratoire Sciences et Ingénierie de la Matière Molle, PSL Research University, UPMC Univ Paris 06, ESPCI Paris, UMR 7615 CNRS, 10 rue Vauquelin, 75231 Paris Cedex 05, France