As a logical extension, many materials are studied and characterized with regard to their self-healing and -recovering properties. As outlined in the first section on tough hydrogel mechanics, this is done by conducting cyclic tensile tests (Figure ). The system with the best damping capacity is represented by the PAAm/CS-Cit 3-double network, where a total energy of W hys = 9 MJ/m 3 was dissipated upon a single tensile cycle (ε = 350%). In contrast, the system with the lowest hysteresis energy and quasi-elastic behavior was reported by Lei et al. with their self-assembling protein-based hydrogels. The latter showed negligeable hysteresis, despite being stretched to a sizable strain of ε = 1000% (much like Figure ). When cyclic tensile tests were performed on tough hydrogels, the hysteresis recovery spanned 10-90% (along with tested strains in the range of ε = 20-1000%), which makes it difficult to compare individual data sets. Furthermore, the majority of the reported data lied in a much smaller range of h r = 20-40%, which reveals the current limitations of self-healing and -recovery independent of the material's improved (fracture) mechanical properties. One notable system with excellent hysteresis recovery was the zwitterionic hydrogel based on sulfobetaine and DMAEA-Q as reported by Gong and co-workers. Here the hysteresis recovery reached h r = 93% at a maximum strain of ε = 350% (much like Figure ).