Robust PAM/HACC dual-network hydrogel with hydroxylated carbon nanotubes for strain sensing and electromagnetic interference shielding

To address the rising need for multifunctional integration in core materials for flexible wearable electronics, this study presents a composite hydrogel that combines high mechanical strength, sensitive sensing capabilities, and efficient electromagnetic interference (EMI) shielding. By incorporating hydroxylated multi-walled carbon nanotubes (OH‑MWCNTs) as nano‑conductive fillers into a polyacrylamide/quaternary ammonium chitosan (PAM/HACC) dual‑network matrix, a multifunctional composite material was successfully fabricated. The PAM/HACC dual‑network structure provides remarkable mechanical properties through synergistic energy dissipation, achieving a tensile strength of 435 kPa and an elongation at break exceeding 2500%. Uniformly dispersed OH‑MWCNTs establish a robust and stable three‑dimensional conductive network within the hydrogel, enabling the material to function as a highly sensitive strain sensor (with GF up to 16.04 at 200%-300%) for reliably monitoring diverse human physiological activities-from large‑scale joint movements to subtle motions such as speech and coughing. Moreover, the hydrogel exhibits an electromagnetic shielding effectiveness exceeding 30 dB, and the average effectiveness is stable at more than 25 dB across the X‑band (8.2–12.4 GHz). This work offers an innovative and promising material platform for next‑generation flexible electronics that integrate sensing and shielding functionalities.