Engineering versatile bi-network ionic conductive hydrogels wearable sensors via on demand graft modification for real-time human movement monitoring

With the rapid development of the field of flexible electronics, it is necessary to develop more new flexible sensor materials with a high degree of flexibility, stretchability, biosafety, and good electrical conductivity to better achieve wearable with the human body. Cellulose hydrogels are promising building blocks for flexible sensors due to their renewability and excellent mechanical strength properties. In this study, we demonstrate an imidazolium ionic cellulose/polyacrylic acid hydrogel (ILHPMC/PAA) with high flexibility, antimicrobial properties and electrical conductivity. Firstly, epoxidized imidazole ionic liquids were synthesized using methyl imidazole as raw material, and imidazole ionic cellulose was prepared by grafting modified hydroxypropyl methyl cellulose (HPMC). Imidazolium ionic cellulose hydrogels were prepared by one-step cross-linking and forming a copolymeric bi-network with acrylic acid according to the principle of free radical polymerisation. This hydrogel has high flexibility, stretchability, biocompatibility, and desired electrical conductivity due to the introduction of imidazole ions, and the sensing sensitivity factor (GF) reaches 6.83. The tensile strength can be up to 1.2 MPa, and it also has excellent antibacterial properties, with an antibacterial zone diameter of up to 29.25 mm. This provides insights into the development of cellulose-based sustainable sensing hydrogel sensors for wearable ionic conductive sensing.