Toward next-generation wearable sensors based on MXene hydrogels

With the rapid advancement of electronic and information technologies, such as artificial intelligence, medical monitoring, virtual reality, and human-machine interaction, flexible wearable sensors have gained increasing importance for future smart life. Hydrogel materials have garnered widespread attention in the realm of wearable sensors due to their three-dimensional biomimetic structure, flexibility, biocompatibility, and other advantageous properties. However, current hydrogel sensors suffer from issues such as low conductivity, mechanical degradation, and water loss. By introducing two-dimensional transition metal carbides and nitrides, so-called MXenes, to hydrogels, the MXene hydrogels are expected to show high electrical conductivity and excellent mechanical strength. Here in this manuscript, the design principles of MXene hydrogels are discussed in detail, together with strategies for enhancing the hydrogels' electrical and mechanical properties toward next-generation wearable sensors. Challenges and potential applications, especially in strain sensors, pressure sensors, temperature sensors, biosensors, humidity sensors, etc., are provided. This work is expected to provide insightful instructions for designing advanced hydrogel sensors. Here in this review, we systematically analyze the design principles of MXene hydrogels for next-generation wearable sensors. Emphasis is placed on multiple wearable sensors based on MXene electrical/mechanical enhancement in the hydrogel network.