A sustainable approach for harnessing the synergy between lignosulfonate and hemicellulose: Towards next-generation bio-derived flexible electronics

The preparation of high-performance conductive hydrogels from renewable and biodegradable materials has received widespread attention in the development of soft electronic devices. However, challenges remain in effectively balancing the functionality, conductivity and mechanical stability of hydrogel-based flexible systems. Enlightened by the synergistic interactions between two naturally abundant biopolymers, lignosulfonate (LGS) and hemicellulose (HCL), a robust and highly conductive LGS-HCL hydrogel was prepared in this study by using LGS, HCL, acrylic acid (AA) and AlCl₃. A dynamic redox process involving Al³⁺/Al²⁺ and hydroquinone/quinone couple triggered the rapid exothermic polymerization reaction under the influence of ammonium persulfate (APS). Effective hydrogen and metal-coordination bonds between LGS, HCL, polyacrylic acid (PAA) and Al³⁺ endowed the hydrogel with exceptional mechanical properties. A maximum tensile strength of ∼0.501 MPa at an elongation of 1089 % and a maximum compressive strength of ∼0.962 MPa with the highest stretchability of 70 % were demonstrated by the synthesized hydrogel. The wearable LGS-HCL hydrogel-based strain sensor can monitor various human motions with a tunable conductivity (up to 5.02 S·m⁻¹), a high sensitivity (a maximum gauge factor of 2.48) and long cyclic stability (500 cycles). In addition, the supercapacitor device, assembled from the polyaniline (PANI)@carbon cloth (CC) electrodes and the LGS-HCL hydrogel electrolyte, exhibited specific capacitance (C_s), highest energy density (E_d) and power density (P_d) of 379.3 F·g⁻¹, 33.71 Wh·kg⁻¹ and 3.20 kW·kg⁻¹, respectively. This work paves the way for the integration of renewable, biodegradable materials in the next generation of sustainable and high-performance flexible electronic devices.