Polydopamine-modified cellulose nanofiber composite hydrogel with strong toughness and high adhesion for human motion detection and wireless sensing

The toughness and adhesiveness of composite hydrogels play an important role in the field of wearable sensors, where they are used due to their remarkable flexibility and diverse specialized properties. In this work, a composite hydrogel with strong toughness and high adhesion for human motion detection and wireless sensing was obtained. Polydopamine (PDA)-modified cellulose nanofibers (PCNFs) were introduced into a polyvinyl alcohol (PVA) and polyacrylamide (PAM) network, resulting in the fabrication of a PCNF/PVA-PAM composite hydrogel. Lithium chloride served as a crosslinking agent and provided conductive ions, and the PCNFs provided the composite hydrogel with strong toughness and adhesion abilities. The compression strength of the obtained PCNF/PVA-PAM composite hydrogel was 1.1 MPa, and its adhesion strength to glass was 63.8 kPa. Moreover, the composite hydrogel exhibited good anti-freezing properties. The compression sensitivity of the composite hydrogel was 1.29, and it still maintained stability even after 500 testing cycles. The strain-sensing abilities of the composite hydrogel were satisfactory for different human body parts. This composite material holds great promise in the fields of wearable devices and wireless signal transmission.