Tough Hydrophobic Hydrogels for Monitoring Human Moderate Motions in Both Air and Underwater Environments

Hydrophobic hydrogels with high strength and great stretchabilityhold immense potential in various fields, such as soft robots, 3Dprinting, and flexible sensors. However, the formation of large hydrophobicdomains in a hydrophobic hydrogel can lead to a heterogeneous structurein the bulk hydrogel. This phenomenon will result in the hydrophobichydrogel becoming opaque, having a large energy hysteresis duringstretching, poor strain-sensitivity, and slow self-recovery. In thisstudy, we successfully developed a series of transparent hydrophobichydrogels that exhibit excellent mechanical properties (low hysteresisand high toughness of & SIM;1.8-2.5 MJ m(-3)) with a desirable strain-sensitivity. The key factor in achievingthis was the ability to tune large, inhomogeneous hydrophobic structuresinto small, well-ordered domains at the scale of 16.50-52.08nm by introducing a small number of electrostatic groups into thehydrophobic networks. The hydrophobic hydrogels were able to formstrong dual physical interactions, including electrostatic interactionsand hydrophobic associations, making them ideal materials for fabricatingwearable sensors with both in air and underwater applications. Thisfacile and effective approach provides a novel method to prepare hydrophobichydrogels with good mechanical performance, low hysteresis, and goodstrain-sensitivity, opening up new potential for their applicationsin various fields.