Adhesive conductive wood-based hydrogel with high tensile strength as a flexible sensor

Conductive hydrogels have promising applications for flexible strain sensors. However, most hydrogels have poor tensile strength and are susceptible to damage, significantly impeding their potential for further application. Wood has been used to reinforce hydrogels, significantly enhancing their strength and dimensional stability. However, wood-based hydrogels generally lack adhesive properties or exhibit low self-adhesion. To address this issue, we introduced acryloyloxyethyltrimethyl ammonium chloride (DAC) into the hydrogel network through graft aggregation. The resulting electrostatic interactions significantly enhanced the adhesion of the wood-based hydrogel up to 270 kPa (for glass) and concurrently strengthened its cohesion. The prepared novel wood-based hydrogel (WDDH) exhibited high tensile strength (3.38 MPa), low-swelling ratio (only 2 % longitudinal), and high tensile strain (274.40 %). When WDDH was used as the wearable strain sensor, it showed a gauge factor of approximately 4.94. The device effectively captured and detected human movements, including finger and joint flexion, walking patterns, and hydration habits. The objective of this research is to develop a wood-based hydrogel with enhanced mechanical strength, adhesive properties, and flexibility for use in wearable sensors. This study provides insight into the development of flexible sensor hydrogels with improved adhesion properties using biomass materials.