Inspired by the hard-shelled pangolins, a bionic hydrogel structure with hard nano silver armor and soft interior was fabricated with outstanding tensile strength and toughness, excellent electrical conductivity and good antibacterial properties.

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Hydrogels with excellent mechanical properties and high conductivity are key materials for the development of flexible electronic devices, smart soft robots, and so forth. However, the preparation of high-performance conductive hydrogels remains a challenge. Enlightened by the strengthening mechanism of skeletal muscles, a green muscle-like conductive hydrogel was prepared through a repeated mechanical training process. Using cellulose nanofibrils (CNFs) as the fiber reinforcing source, partial depolymerized enzyme hydrolyzed lignin as the interfacial binding agent, and Ag+ as the conducting medium in a polyvinyl alcohol (PVA) matrix, the prepared composite hydrogel exhibited anisotropic high strength, high toughness, and excellent conductivity. Through the introduction of double physical enhancement networks and the adoption of a mechanical training method that mimics the muscle strengthening principle, the enhancement effect of CNFs was maximally demonstrated in the PVA composite hydrogel. Meanwhile, this study also provides a new and effective reference for the preparation of high-performance green hydrogels.

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An ultra-tough conductive composite hydrogel with antibacterial activity and UV-shielding performance was prepared via a simple soaking approach. The soaking agent TA@LS-Ag was synthesized via a simple microwave-assisted reduction method using the green biomass tannic acid (TA) and sodium lignosulfonate (LS) as the carrier for silver nanoparticles (Ag NPs). The TA@LS-Ag/PVA composite hydrogel was then prepared by soaking the pure poly­(vinyl alcohol) (PVA) hydrogel into the TA@LS-Ag suspension. The dense hydrogen bonding interactions between the hydroxyl groups in the PVA chain and oxygen-containing groups in TA@LS-Ag endowed the composite hydrogel with excellent mechanical properties, including great tensile strength (5.43 MPa), high toughness (30.51 MJ/m3), and outstanding crack resistance performance. The composite hydrogel also exhibited good electrical performance with high conductivity (4.1 S/m) and favorable sensitivity to stretch, compression, bending, and handwriting. In addition, the composite hydrogel exhibited excellent antibacterial activity and UV-blocking property. This study provides a feasible approach for fabricating multifunctional hydrogels, integrating the good mechanical performance with high conductivity, electric sensing, and excellent antibacterial activity for promising flexible electronic applications.