MXene-integrated Printed Piezoelectric Flexible Sensors: A Breakthrough in Real-time Monitoring for Medical and Smart Applications

As an emerging 2D transition metal carbide material with a layered structure and high metal-liked conductivity, MXene exhibits significant potential for application in pressure monitoring. Nevertheless, it remains a great challenge to achieve excellent response sensitivity, high response intensity, structural stability, and oxidation resistance for the MXene-based pressure sensors. Herein, based on the template-directed growth strategy, we realized the assisted deposition of the Ag nanoparticles between the layers of the waffle-structured MXene, preparing the chocolate-inlaid Ag@waffle-structured MXene (WSM-A8). Utilizing the DFT calculation, the theoretical analysis of the transition of the energy bands and the increase of the charge density was conducted for the WSM-A8. With the finite element analysis, the establishment of the conducting pathways in the WSM-A8 was systematically simulated. The construction of the oriented field-modulation piezoelectric structure proposed in this study is verified. The pressure sensor prepared in this work presents the highest ΔI/I ₀ response intensity (507 in 210 kPa) among the reported MXene-based piezoelectric sensors with a satisfactory sensitivity (45/30 ms for response/recovery time). Meanwhile, the pressure sensor possesses outstanding structural stability (less than 4% attenuation of the response value after 500 bending cycles) and superior oxidation resistance. Furthermore, we successfully integrate the sensor with a convolutional neural network (CNN)-based machine learning algorithm for intelligent letter recognition and wireless plantar pressure monitoring, achieving high recognition accuracy. This study provides a feasible approach for achieving reliable real-time pressure monitoring, demonstrating great potential in medical diagnosis, intelligent actuators, and human-computer interactions.