Tannic\nAcid–Silver Dual Catalysis Induced Rapid\nPolymerization of Conductive Hydrogel Sensors with Excellent Stretchability,\nSelf-Adhesion, and Strain-Sensitivity Properties

Abstract

The\napplication of conductive hydrogels in intelligent biomimetic\nelectronics is a hot topic in recent years, but it is still a great\nchallenge to develop the conductive hydrogels through a rapid fabrication\nprocess at ambient temperature. In this work, a versatile poly­(acrylamide)\n@cellulose nanocrystal/tannic acid–silver nanocomposite (NC)\nhydrogel integrated with excellent stretchability, repeatable self-adhesion,\nhigh strain sensitivity, and antibacterial property, was synthesized\nvia radical polymerization within 30 s at ambient temperature. Notably,\nthis rapid polymerization was realized through a tannic acid–silver\n(TA-Ag) mediated dynamic catalysis system that was capable of activating\nammonium persulfate and then initiated the free-radical polymerization\nof the acrylamide monomer. Benefiting from the incorporation of TA-Ag\nmetal ion nanocomplexes and cellulose nanocrystals, which acted as\ndynamic connecting bridges by hydrogen bonds to efficiently dissipate\nenergy, the obtained NC hydrogels exhibited prominent tensile strain\n(up to 4000%), flexibility, self-recovery, and antifatigue properties.\nIn addition, the hydrogels showed repeatable adhesiveness to different\nsubstrates (e.g., glass, wood, bone, metal, and skin) and significant\nantibacterial properties, which were merits for the hydrogels to be\nassembled into a flexible epidermal sensor for long-term human–machine\ninterfacial contact without concerns about the use of external adhesive\ntapes and bacterial breeding. Moreover, the remarkable conductivity\n(σ ∼ 5.6 ms cm^–1) and strain sensitivity\n(gauge factor = 1.02) allowed the flexible epidermal sensors to monitor\nvarious human motions in real time, including huge movement of deformations\n(e.g., wrist, elbow, neck, shoulder) and subtle motions. It is envisioned\nthat this work would provide a promising strategy for the rapid preparation\nof conductive hydrogels in the application of flexible electronic\nskin, biomedical devices, and soft robotics.