Highly stretchable and self-healing cellulose nanofiber-mediated conductive hydrogel towards strain sensing application

Hypothesis Hydrogel-based sensors have attracted considerable attention due to potential opportunities in human health monitoring when both mechanical flexibility and sensing ability are required. Therefore, the integration of excellent mechanical properties , electrical conductivity and self-healing properties into hydrogels may improve the application range and durability of hydrogel-based sensors. Experiments A novel composite hydrogel composed of polyaniline (PANI), polyacrylic acid (PAA) and 2,2,6,6-tetramethylpiperidin-1-yl)oxyl (TEMPO)-oxidized cellulose nanofibrils (TOCNFs) was designed. The viscoelastic, mechanical, conductive, self-healing and sensing properties of hydrogels were studied. Findings The TOCNF/PANI/PAA hydrogel exhibits a fracture strain of 982%, tensile strength of 74.98 kPa and electrical conductivity of 3.95 S m −1 , as well as good mechanical and electrical self-healing properties within 6 h at ambient temperature without applying any stimuli. Furthermore, owing to the high sensitivity of the TOCNF/PANI/PAA-0.6 hydrogel-based strain sensor (gauge factor, GF = 8.0), the sensor can accurately and rapidly detect large-scale motion and subtle localized activity. The proposed composite hydrogel is as a promising material for use as soft wearable sensors for health monitoring and smart robotics applications.