Stretchable and self-healing polyvinyl alcohol/cellulose nanofiber nanocomposite hydrogels for strain sensors with high sensitivity and linearity

The development of wearable strain sensors with high sensitivity, linearity and self-healing property is highly demanded. Herein, a simple yet efficient solution compounding method is proposed for fabricating a cellulose nanofiber reinforced borax/polyvinyl alcohol nanocomposite hydrogel (CBPH). The resultant CBPH exhibited largely enhanced ultimate tensile strength (47.1 kPa) and high toughness (213.9 kJ m−3) compared with that of neat borax/polyvinyl alcohol hydrogel (3.4 kPa, 44.3 kJ m−3), ascribing to efficient load transfer between dynamically hydrogen-bonded cellulose nanofiber and polyvinyl alcohol. Besides, dynamic borate-diol bonds among the CBPH contributed to self-healing performance with a healing efficiency reaching nearly 60%. Due to its large stretchability, high toughness and favorable ionic conductivity, the CBPH was used as a stretchable and self-healing ionic conductor for assembling a wearable strain sensor, showing a high yet linear sensitivity (~1.86) over a wide strain range of 0–100%, fast response time (<240 ms) and stable signal feedbacks for human motion detection.