Acrylic acid incorporated nanocellulose/acrylamide ion-conductive hydrogels for wearable sensors

In this paper, CNC/PAM/PAA interpenetrating network composite hydrogels were prepared from acrylamide (AM), cellulose nanocrystals (CNC), and acrylic acid (AA) by in situ free radical polymerization. CNC/PAM/PAA-Ca2+ hydrogels were successfully prepared by adding CaCl2 to the mixed solution to introduce ions. The composite hydrogels were characterized using scanning electron microscopy and Fourier transform infrared spectroscopy and tested for their mechanical, electrical, and sensing properties. The experimental results showed that the copolymerization reaction of AM and AA resulted in hydrogels with excellent mechanical properties, with a maximum tensile strength of 98.7 kPa and an elongation at break of 643.6%. In addition, the introduction of Ca2+ ions significantly improved the conductivity and sensitivity of the hydrogel. The developed multifunctional poly (AM-AA) hydrogels were able to stably detect the relative changes in electrical resistance during cyclic tensile, compressive, and bending motions of a human finger, which is expected to be widely used in flexible sensor devices.