Wood Engraving Picture-inspired Wearable Flexible Hydrogel Sensors Enabled by Conformal Polyvinyl Alcohol/MXene Composite Ink.

Flexible hydrogel sensors show great utilization potential in the development of wearable devices. Nevertheless, issues such as unsatisfactory sensitivity, intricate fabrication processes, and substantial cost continue to impede their widespread application. Furthermore, a significant challenge resides in developing a convenient method to mold the flexible hydrogel into a variety of shapes, thereby fulfilling the different scenario requirements. Herein, we report a cost-effective, multifunctional polyvinyl alcohol (PVA)/multilayer MXene composite PMI hydrogel, which is crosslinked by the addition of sodium tetraborate with the dynamic benzyl boronate ester crosslinking for next-generation wearable sensors. It shows good real-time detection capability in human movement and physiological signal monitoring, as well as speech recognition. However, the plasticity of the aforementioned hydrogel still fails to meet the requirements for the preparation of finely patterned sensors. Inspired by the preparation process of wood engraving pictures, we develop a two-step strategy to fabricate different complex shapes of wearable flexible hydrogel sensors: (1) utilizing thick PVA/MXene precursor ink to create different complex patterns with high resolution; (2) spraying sodium tetraborate solution to fix the patterns quickly. Based on this method, we further explore the application of PMI hydrogel sensors as a flexible wearable device to achieve remote gesture control of the driving paths of car and ship models. Our study strongly demonstrates the promising development potential of PMI hydrogel in the field of flexible wearable human-technology interaction.