Fe-TA-mediated self-catalytic fabrication of dual-crosslinked cellulose-based hydrogels and their highly sensitive strain sensing properties

To address the issues of energy-consuming fabrication, poor mechanical properties, and low sensing sensitivity of conventional hydrogel sensors, this study reports the development of an iron-tannic acid (Fe-TA)-mediated autocatalytic strategy for the rapid construction of “covalent-ionic” dual-crosslinked cellulose-based hydrogels. This system spontaneously generates radicals at room temperature through the redox cycle of Fe-TA and ammonium persulfate, driving the polymerization of carboxymethyl cellulose (CMC) with acrylamide to achieve ultrafast in-situ formation of the hydrogel within 119 s. By introducing carboxylated cellulose nanofibers (CCNFs) and utilizing Fe 3 + ion coordination, a dual-crosslinked network hydrogel (denoted as CAMFFE hydrogel) was constructed, leading to markedly improved mechanical properties with a compressive strength of 386 kPa and an elongation at break of 528%. Benefiting from the multifunctional integration of Fe 3+ (catalysis, crosslinking, and conductivity), this hydrogel strain sensor exhibits high sensitivity with a gauge factor (GF) ranging from 1.46 to 4.16, and rapid response (0.3 s) and recovery (0.5 s) over the strain range of 0–500%, along with strong adhesion to substrates such as wood and skin (up to 85.7 kPa). The study further demonstrates its versatile applications in human motion monitoring and wireless handwritten recognition, providing new materials and valuable design insights for the development of high-performance, sustainable flexible electronic devices.