Multifunctional conductive hydrogels based on the alkali lignin-Fe³⁺-mediated Fenton reaction for bioelectronics

Requirements for sustainable development have led to the urgent need for low cost, green, and reproducible resources. Lignin is one of the resources meeting this requirement. Herein, an alkali lignin (AL)-Fe³⁺-H₂O₂ autocatalytic system was introduced to assemble multifunctional AL-Fe³⁺/polyacrylic acid (PAA) hydrogels. The AL-Fe³⁺ pair-mediated Fenton reaction can generate a large number of free radicals to accelerate gelation. Owing to the abundant hydrogen bonds and metal coordination bonds, the AL-Fe³⁺/PAA hydrogels possessed excellent mechanical properties (tensile strength of 38 kPa), adhesion properties (18 kPa for pigskin), and self-healing ability (78 % for tensile strength and 88 % for tensile modulus). In addition, hydrogel-based sensors with high durability, strain sensitivity, and fast response times were employed to accurately monitor motion or electrophysiological signals. Subsequently, a portable sensing device for the wireless and remote monitoring of a user's motion status was integrated. As a result, an AL-Fe³⁺-H₂O₂ autocatalytic system has great potential for use in hydrogel preparation in flexible bioelectronics and wearable sensors. It can promote the sustainable development of flexible bioelectronics.