Enhanced interface bonding of hydrophobic encapsulated hydrogel fibers by mechanical interlocking structure: Toward anti-drying and anti-swelling strain sensors

[Display omitted] •Continuous high-strength hydrogel fibers were encapsulated with silicone rubber.•Amphiphilic stearic acid was embedded to enhance the interface bonding.•Composite hydrogel fibers have excellent anti-drying and anti-swelling properties.•The composite hydrogel fiber showed an excellent underwater sensing performance. Conductive hydrogel fibers with superior mechanical and electrical performance have been developed for flexible wearable electronics, but the inherent properties of hydrogels for dehydration in the atmosphere and underwater swelling limit its widespread application. In this work, a silicone rubber encapsulated hydrogel fiber with enhanced interface bonding, excellent mechanical and electrical properties was successfully developed, in which the core polyvinyl alcohol/sodium alginate hydrogel fiber was prepared by a continuous wet-spinning and the following freeze-thawing. The interlocking dual-network structure and the improved ion transport by negatively charged sodium alginate gave the core hydrogel fiber excellent strength of 4.15 MPa, elongation-at-break of 1531 % and electrical conductivity of 17.01 S·m−1. After encapsulation using a silicone rubber, the composite hydrogel fiber showed a low expansion rate underwater for 7 days of 1.00 ± 0.21 % and low weight loss in the air over 36 h of 38.67 ± 0.38 %. And the interface bonding of the core hydrogel fiber and silicone layer was enhanced by the bridging effect of amphiphilic stearic acid. Therefore, the composite hydrogel fiber demonstrated a great potential as a strain sensor for underwater communication to ensure the safety of individuals in an underwater environment.