"Muscle is the natural contractile system that artificial systems attempt to emulate.” . This presentation is based on a paradigm: "living matter realizes motions at almost no stress". You can experiment by yourself by flexing your forearm: two large muscles, the biceps and the triceps, will change their shapes by a large amount, the shape-changes are not isotropic at all, but are isochoric—long, slender shapes transform into short, broad ones, and vice versa; more important, your forearm will not spring back to any preferred configuration, meaning that muscles are not storing any elastic energy whatsoever. Our goal is to put forward a theoretical framework to improve our ability to produce controlled motions of soft materials, by mimicking natural muscles. Most of our investigations originated as a question: is it possible to have very large, non-isotropic, shape-changes of a deformable body without varying its elastic energy? The answer is yes: soft matter exhibits noticeable morphological changes, which may arise as a consequence of many different ‘actuations’. Our involvement dates back to the seminal paper  that prompted us a thoroughly study of non-linear elasticity with large, evolving distortions. At first, we proposed the use of the notion of large distortions as a modeling tool for soft material ; since then, the same tool proved very useful in modeling apparently disparate phenomena such as muscle contractions, , director reorientations in nematic elastomers , phase transitions in nematic gels [6, 7], actuation of Ionic Polymer Metal Composites . A distinctive attribute for all these phenomena is that large displacements are triggered by evolving distortions; moreover, it is possible to realize, through distortions, very large shape changes at no, or low, change of the elastic energy . References  G. Pollack. Cells, Gels and the Engines of Life. Ebner & Sons, (2010).  A. DiCarlo, S. Quiligotti. Mechanics Research Communications 29, pp449–456 (2002).  P. Nardinocchi, L. Teresi. Journal of Elasticity, 88, pp27–39 (2007).  A. Evangelista, P. Nardinocchi, P.E. Puddu, L. Teresi, C. Torromeo, V. Varano. Progress in Biophysics and Molecular Biology, 107, pp.112–121 (2011).  A. DeSimone, A. DiCarlo, L. Teresi. European Physical Journal E, 24, pp.303–310 (2007).  Y. Sawa, K. Urayama, T. Takigawa, A. DeSimone, L. Teresi. Macromolecules 43, pp.4362–4369 (2010).  L. Teresi, V. Varano. Soft Matter, in press (2013).  P. Nardinocchi, M. Pezzulla, L. Placidi. Journal of Intelligent Material Systems and Structures, v.22/16, pp.1887–1897 (2011).  P. Nardinocchi, L. Teresi, V. Varano. J. Mechanics Physics of Solids, n.60, pp.1420- 1431 (2012).
Lucantonio, A., Nardinocchi, P., Pezzulla, M., Pugliese, V., Teresi, L. (2013). Modeling Tools for Soft Robotics.