Preparation of chitosan quaternary ammonium salt-sodium alginate/poly acrylic acid hydrogel and its application in flexible sensing

Flexible strain sensors have become key devices in the field of emerging technologies due to their excellent stretchability, conformal contact with substrates, and stable electrical response under dynamic deformation. The core to improving their performance lies in rational material selection and structural design. Biomass-derived composite hydrogels are highly promising biomimetic platforms, integrating flexibility, tunable conductivity, and tailorable mechanical properties while meeting the requirements of sustainable development. In this study, quaternized chitosan (QCH)-a derivative of natural chitosan-was used as the matrix to fabricate two types of double-network (DN) hydrogels: one being QCH-sodium alginate/polyacrylic acid (QCH-SA/PAA) crosslinked with macromolecular sodium alginate (SA), and the other QCH-sodium citrate/polyacrylic acid (QCH-CA/PAA) crosslinked with small-molecule sodium citrate (CA). Under optimized conditions, the QCH-SA/PAA hydrogel exhibited superior mechanical robustness compared to the QCH-CA/PAA hydrogel, achieving a tensile strength of 1236 kPa, a compressive strength of 1018 kPa, along with excellent strain sensing performance (ΔR/R₀ = 0.44), a high swelling ratio (77 g/g), and rapid self-healing (97.03 % recovery in 30 min). This work establishes a sustainable DN hydrogel fabrication route, clarifies the mechanical enhancement mechanism of macromolecular crosslinkers, and develops a high-strength multifunctional hydrogel, advancing the application of biomass materials in next-generation flexible electronics.