Ion-based double network hydrogel with compressive, conductive, and sensing properties for sports monitoring

Conductive hydrogel, as a promising candidate material, is ideal for multifunctional strain sensors due to its similarity to biological tissues. It offers good wearability and high-precision information acquisition. However, fabricating conductive hydrogel-based strain sensors with both superior mechanical and conductive properties remains challenging. In this study, a compressive and conductive strain sensor based on multi-dynamic interactions is fabricated through a simple strategy. The strategy exploits hydrogen bonding and ionic ligand bonding by using nanocellulose reinforced poly(acrylic acid) hydrogels impregnated with the Fe3+ solution to prepare a double-network hydrogel. The prepared PAA/CNF–Fe3+ double-network hydrogel exhibited excellent properties, including extraordinary performance compressive stress (2.96 MPa) and remarkable electrical conductivity (6.34 S/m). With these advantages, the PAA/CNF–Fe3+ double network hydrogel was developed to be an attractive strain flexible sensor with cyclic stability (150 cycles) and good strain sensitivity (GF = 2.87). In addition, the PAA/CNF–Fe3+ hydrogel flexible sensor can be used as an electronic skin to accurately discriminate subtle and large body movements. Given the simple strategy, double network structure, and satisfactory functionality, the PAA/CNF–Fe3+ hydrogel provides a new sustainable and multifunctional development strategy that can be applied in the field of strain sensors and medical detection.