1. Open
Laboratory on Experimental Micro and Nano Mechanics,
Institute of Mechanics, Bulgarian Academy of Sciences, Acad. G. Bonchev Street, Block 4, 1113 Sofia, Bulgaria
2. CNRS,
Institut de Chimie de la Matière Condensée de Bordeaux, Universitè de Bordeaux, 87 Av. du Dr. Schweitzer, 33608 Pessac Cedex, France
3. Department
of Earth, Life and Environment Sciences (DiSTeVA), University of Urbino, Via Ca’ Le Suore 2/4, 61029 Urbino, Italy