Hierarchically crosslinked ionic nanocomposite hydrogels with ultrahigh mechanical properties for underwater bioinspired capturing device

Various applications of nanocomposite hydrogels with a single crosslinked network have been largely limited by their poor comprehensive mechanical properties, despite their prominence in certain mechanical properties. Here, we introduce ferric ions into titania-based nanocomposite hydrogels to fabricate robust ionic nanocomposite hydrogels (INC gels) with hierarchically crosslinked networks. The introduction of ion crosslinkers into nanocomposite hydrogels dramatically improves their comprehensive mechanical properties. The mechanical attributes can be changed over wide ranges by adjusting hydrogel components and the optimal INC gel exhibits the super high strength of 13.0 MPa, elastic modulus of 26.8 MPa, and toughness of 34.3 MJ m⁻³. In addition, The INC gels show a good mechanical and volume stability in saline solutions due to the unique crosslinked network. The reversible phase separation in gels can be used for the achievement of the shape memory effect without significantly destroying the mechanical properties and enable the mussel shell-like hydrogel to imitate the self-protection behaviour of the mussel to grab the bead underwater. Therefore, these hydrogels will hold a great potential in underwater mechanical catching hands.