Anagrafe della ricerca

Nature has always been a source of inspiration for scientists and the in-depth study of natural systems requires an interdisciplinary approach. In the animal kingdom, insects, fish, reptiles and amphibians are considered relatively simple living beings. However, they have developed extremely specialized survival strategies across the eras, by evolving, selecting and adapting their structures to optimize specific functions, thus exhibiting disparate and sometimes astonishing abilities that allow them to improve locomotion, adhesion, growth and repair processes in unparalleled ways, adapting to extreme environments and to escape predators. Salamanders are prominent among these animals with extreme capabilities. These extraordinary amphibians have already inspired advanced bio-mimetic robots for their uncommon ability to switch to three-fold locomotion modes, allowing efficiently land and water displacements by coordinating leg movements and spinal undulations. In particular, axolotls –a neotenic salamander species– are unique adult vertebrates able to regenerate entire limbs and an impressive repertoire of complex structures and organs, that have great interest in regenerative biology and medicine. Additionally, the axolotl skin is also the sole known biological material (except for the cow mammary gland) to be auxetic, i.e. having a Negative Poisson Ratio (NPR). This counter-intuitive mechanical property is extremely infrequent in living structures and essentially encountered only in man-made foams, re-entrant truss-like micro-structures and artificial wrapped fabrics. Surprisingly, although NPR is very rare in nature, it remains to be understood which advantages could be gained by axolotls from skin auxeticity. Therefore, starting from preliminary analyses and recent literature, the Project AMPHYBIA aims to theoretically investigate, by using nonlinear elasticity applied to growing continua and the expertise on bioinspired metamaterials of the applicants, how the special locomotion and regeneration capabilities of axolotls could be significantly enhanced by their auxetic skin. Preliminary calculations indicate NPR as a key factor in minimizing both the residual stresses accompanying tissue (re)growth and deviatoric elastic energy cyclically stored during movement, with direct effects on scar-free healing processes and on some as yet unexplained mechanisms of autotomy. By exploring the link between the skin auxeticity and unique axolotl skills, the project could contribute to a different (physical and biomechanical) view of the multiscale interplay among cellular mechanisms, growth and tissue mechanical properties, with potential implications in conceiving new classes of bio-inspired self-repairing, wrinkling-free and fatigue-evading metamaterials.