Rapid Construction of β-Cyclodextrin-Functionalized Carbon Nanotubes Semi-Interpenetrating Hydrogels for Flexible Sensors

Conductive hydrogels hold great promise for applications in flexible sensors. However, for such soft hydrogel systems, achieving a synergistic integration of high mechanical robustness, excellent conductivity, and outstanding self-healing capability remains a significant challenge. To address this issue, this study introduces β -cyclodextrin-functionalized multi-walled carbon nanotubes ( β -CD@MWCNTs) combined with a dynamic redox initiation system undergoing rapid polymerization to prepare hydroxyethyl cellulose/polyacrylic acid/ β -CD@MWCNTs (HEC/PAA/ β -CD@MWCNTs) semi-interpenetrating network hydrogels. The incorporated β -CD@MWCNTs serve as additional physical crosslinking points within the system, which not only markedly enhance the mechanical properties of the hydrogel—including fracture strain (1407.28%), toughness (734.71 kJ m −3 )—while retaining the low modulus (13.08 kPa) characteristic of typical hydrogels, but also confer a remarkable self-healing capability (with up to 88.65% healing efficiency for elongation at break). Furthermore, β -CD@MWCNTs can form a stable ion-electron synergistic conductive pathway with Fe 3+ , endowing the hydrogel with excellent electrical conductivity (37.21 mS cm −1 ) and high strain sensitivity (gauge factor [GF] = 3.77). This study introduces functionalized carbon nanotubes, providing a novel strategy for developing high-performance conductive hydrogels that combine low modulus with high stretchability, excellent conductivity, and self-healing capability, underscoring their broad application potential in flexible sensing including human motion monitoring, information encryption, and handwriting anti-counterfeiting.