Tough hydrogel–elastomer hybrids hydrophobically regulated by an MXene for motion monitoring in harsh environments

The hydrophobic encapsulation method is one of the common methods to ensure the regular operation of electronics under water. However, the hydrogel underwater sensors prepared by hydrophobic encapsulation still suffer from weak interfacial bonding. Here, we developed a high toughness and low hysteresis, dual-physically cross-linked structure hydrogel that was hydrophobically regulated by an MXene. The introduction of an MXene into the hydrogel can not only enhance the conductivity as a conductive filler, but also improve the mechanical properties as a physical cross-linking point. At the same time, the hydrophobic fluorine groups of the MXene can regulate the hydrophobic properties and enhance the bonding strength with the hydrophobic layer. In this way, a hydrophobic encapsulation structure hydrogel–elastomer hybrid was constructed, which showed a maximum bonding strength of 34.19 ± 1 N m−1, and excellent anti-drying (7d, ≤5.5%), and anti-swelling (7d, ≤0.07) properties. Furthermore, the core–shell structure hybrid fiber sensor exhibited excellent conductivity, sensitivity, and long-term stability performance in harsh environments, such as underwater, acid (pH = 1), alkali (pH = 14), salt solution (1 M NaCl), and alcohol solution. It provides a reliable opportunity for underwater smart wearable sensors using hydrogels with high flexibility.