MXene cracked-layer composite sodium alginate/CNC-based hydrogel for robust sensing with high-sensitivity dynamic motion perception

Conductive hydrogel strain sensors with high stretchability, wide sensing range and high sensitivity have been extensively studied for their potential applications in wearable sensing devices. However, achieving high sensitivity in the low-strain range remains a challenge. In this study, the hydrogel was prepared by blending acrylamide, sodium alginate, and cellulose nanocrystals. The hydrogel substrate was fabricated using the electrohydrodynamic printing method, and hierarchical ultraviolet photopolymerization was employed to achieve effective bonding between the hydrogel substrate and MXene film. Further, the hydrogel composite substrate was pre-stretched to overcome the interfacial stress differences between the MXene film and hydrogel substrate, thereby completing the fabrication of a PAAM-SA 2% -CNCs 3% & MXene (PSC&M) sensor with the designed crack structure. The fabricated strain sensor significantly broadened the detection sensitivity of hydrogel sensors in the low-strain range (Strain: 0–5 %, GF = 23.4) and achieved fast response/recovery times (106 ms / 82 ms), obtaining excellent mechanical properties (0.33 MPa stress, 710 % elongation at break) and electrical conductivity (1.931 mS/cm). Application demonstrations based on the fabricated PSC&M sensors in various human motions, subtle vibration signal monitoring and hand-knuckle rehabilitation training, to show their potential applications in smart devices, e-skin and wearable medical rehabilitation devices.