Lignin-optimized MXene/foam pressure sensors with high-sensitivity and robust sunlight sterilization

Abstract

Advanced conductive foams as pressure sensors have substantial potential for wearable devices. Ideal wearable pressure sensors are often expected to simultaneously achieve, such as high sensitivity, wide sensing range, long-term stability, and sterility property. MXene-based flexible pressure sensors have garnered widespread attention in wearable electronics due to its high conductivity, rich surface terminal groups and hydrophilicity. However, the susceptibility of MXene to oxidation seriously weakened the effectiveness of sensors during long-term practical use. In this study, silver nanoparticles decorated alkaline lignin (AL-Ag), MXene and nature rubber latex (NR) are co-foaming to fabricate a flexible pressure sensor. As an inexpensive and abundant industrial byproduct, AL with abundant phenolic hydroxyl group can effectively prevents the oxidation of MXene through its antioxidant ability and the hydrogen bonding interactions with MXene, which exhibits negligible sensitivity attenuation after 30 days’ open placement. The AL-Ag/MXene/NR foam has a great performance in sensing applications, exhibiting both high sensitivity (16.05 kPa⁻¹) and broad response range (0 ∼ 200 kPa), which is better than most reported conductive foams. This foam sensor is capable of monitoring human motion and sensing spatial pressure distribution. Moreover, due to the synergistic antibacterial behaviors of photothermal/ion (Ag⁺@Zn²⁺) effect, the AL-Ag/MXene/NR foam can rapidly realize sterilization under sunlight. This work provides a promising strategy for addressing the stability issues of MXene composites using lignin, which shows a great potential in wearable and motion monitoring fields. This work not only provides a general approach for designing long-term stable MXene-based flexible pressure sensors with high comprehensive performance, but also raise the sustainable high-value utilization of lignin for sensors applications.