Skin-Inspired Tough Elastomer with Moisture-Triggered Switchable Mechanical Properties

Biological tissue usually exhibits good water adaptive mechanical properties, which can maintain high strength and toughness in both wet and dry states. However, synthetic tissue like hydrogel usually becomes hard and brittle in its dry state. Herein, this challenge is met by exploring iron-catechol complex (TA-Fe³⁺ ) as a great platform combining extremely different polymers (elastomer and hydrogel) to construct new tissue-like soft composite materials with two different continuous phases, which have not yet been reported. In its dry state, the xerogel phase becomes a reinforced segment to increase the strength of PB without losing its toughness. In its wet state, this soft material becomes high performance hydrogel, where hydrogel phase absorbs high water and elastomer phase can sustain high loading. Such heterogeneous phase structures provide a good idea for designing the soft materials, exhibiting a trade-off between its high strength and toughness in both wet and dry states. Furthermore, its shape memory behaviors in both its wet and dry state, which shows a great potential application for complex adaptive shape transformation and engineering application like lifting of heavy objects under remote control due to high photo-thermal transition of TA-Fe³⁺ is explored.