A MXene heterostructure-based piezoionic sensor for wearable sensing applications

Humans rely on ion transport to sense and process tactile information. Piezoionic sensor can directly convert mechanical energy into electrical energy through similar ion migration, showing applications in wearable sensing. However, affected by the electrode materials properties, the relatively low voltage output and poor stability of the piezoionic sensors restrict their development. Here, we designed a MXene/Ag nanoparticles heterostructure electrode-based piezoionic sensor with stable and high-performance voltage output. During ion mediated mechanoelectric conversion, the layered MXene nanosheets in electrodes provide transport channels for movable ions. While the interlayer insertion of Ag nanoparticles increases the interlayer spacing between MXene nanosheets, improving the ion storage and transport. Under a bending deformation of 0.7 % strain, the sensor outputs 11.1 mV voltage. The voltage can maintain stable under cyclic deformation for about 13000 s. Based on the excellent mechanical-to-electric conversion, this sensor can be applied to monitor human body activities. The feasibility of the sensor for guiding high-quality cardiopulmonary resuscitation (CPR) training is also demonstrated. Moreover, it can be adhered on the finger to generate pulse or square wave electrical signals by rhythmic bending the finger, which can transmit information based on the coding principle of Morse code. These results indicate the potential of the self-powered piezoionic sensor in medical rehabilitation and human–computer interaction.