Search

• The asymmetric hydrogel is adjusted and assembled by lignin and cellulose derivatives. • The hydrogel exhibits completely asymmetric adhesion, strength, and electriferous. • The hydrogel-based sensor has excellent skin adaptability and application stability. • The hydrogel can be applied to self-adhesive bioelectrodes and self-powered sensors. Mechanical adaptability, great wearability, application stability, and self-powered sensing characteristics are important requirements for hydrogel-based strain sensors. In this study, a novel double-layer hydrogel was fabricated with asymmetrical adhesion, strength, and electriferous properties. Wherein, the lignosulfonate sodium (LS)-borax mediated bottom hydrogel layer exhibits excellent softness (Young's modulus: ~14.2 kPa) and skin-adhesion (Adhesive strength: ~18.7 kPa) while the quaternary hydroxyethyl cellulose (QHEC) mediated top hydrogel layer demonstrates great mechanical strength (Young's modulus: ~101.3 kPa) and non-adhesive (Adhesive strength: ~2.2 kPa) properties. These complementary asymmetrical adhesion and strength properties endow the hydrogel-based sensor with exceptionally stable sensing performance and adaptive wearability; moreover, the lignocellulosic materials utilization plays a significant role in the designability, antibacterial and biodegradable properties. In addition, the synergy of negative LS (-) and positive QHEC (+) particles enables the double-layer hydrogel great self-powered sensing because of the directional movement of free ions initiated by the external mechanical stimulus. This study presents a hierarchical design idea of wearable electronics, which will have potential applications in many fields from wearable bioelectrodes to self-powered sensors. [ABSTRACT FROM AUTHOR]

The restacking tendency of 2D Ti 3 C 2 T X (MXene) sheets is the main obstacle preventing their application as functional materials in hydrogel. Herein, we fabricated novel ultra-stable 3D MXene-polyacrylamide (PAM) nanocomposite hydrogels inspired by the structure of a spider web. In particular, MXene nanosheets were uniformly located in a gel medium by precise alignment of sonication treatments, followed by the in-situ self-assembly of PAM hydrogel. In this instance, the MXene nanosheets are well-confined and trapped (via strong interactions) by the interwoven spider web-like structure of the PAM chains, which grow in-situ on the surface of the nanosheets. This approach proved effective to solve problems associated with the poor stability of MXene nanosheets in the hydrogel; more prominently, the tight cross-linked structure endows the MXene-PAM hydrogel with anti-compressive and anti-swelling capabilities; the continuous distribution of MXene nanosheets connected by the PAM network creates electron transport pathways and proton transport bridges in the hydrogel. Therefore, the hydrogel can be employed as a temperature and strain sensor or as a component of moist-electric nanogenerator. Image 1 • A temporary alignment and permanent in-situ fixation design was proposed. • Spider web-inspired anti-aggregation robust MXene hydrogel was constructed. • The DFT study predicts the formation for the bionic networks. • The hydrogel can be employed as sensor or moist-electric nanogenerator. [ABSTRACT FROM AUTHOR]