1. Université Clermont Auvergne, CNRS/IN2P3, Laboratoire de Physique de Clermont, 4 Avenue Blaise Pascal, 63178 Aubière (Clermont-Ferrand), France
2. Technogym S.p.A., via Calcinaro 2861, 47521 Cesena (FC), Italy
3. Department of Materials, Imperial College London, South Kensington Campus, London, SW7 2AZ, UK