Lignin and cellulose derivatives-induced hydrogel with asymmetrical adhesion, strength, and electriferous properties for wearable 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.

Automated summary

A novel double-layer hydrogel was fabricated with excellent softness and skin-adhesion in the bottom layer, and great mechanical strength and non-adhesive properties in the top layer. The complementary asymmetrical adhesion and strength properties endow the hydrogel-based sensor with stable sensing performance and adaptive wearability, potentially applicable in various fields.