Flexible, biocompatible and highly conductive MXene-graphene oxide film for smart actuator and humidity sensor

The evaporation of water occurs ubiquitously on earth. Hence, smart materials that can directly convert signals generated via water stimulation into mechanical motion have attracted wide attention. However, it is still a challenge to develop novel functional materials with fast response, large scale deformation, and long-term stability for moisture-gradient actuators. Here, a flexible, conductive, layer-structured homogenous Ti3C2Tx MXene-graphene oxide (MGO) film-based moisture-driven actuator and humidity sensor were fabricated. The oxygen groups and d-spacing could be effectively adjusted by MXene/GO composition ratio, thereby tuning the actuation performance. MGO(3) (MXene/GO = 3) displayed a large bending angle, and reversible deformation. And the bending speed of MGO(3) is up to 32 degrees s(-1). Furthermore, MGO(3) actuation displayed long-term stability via suppression of MXene oxidation by the introduction of GO and showed good cycling stability. MGO(3) actuators are constructed, which could mimic the blooming of flower, lifting and carrying objects, and be used as a non-contact control switch. In addition, MGO(3) showed a linear sensitive response to humidity and excellent biocompatibility which make it suitable for respiratory monitoring. This work demonstrated that flexible, biocompatibility and conductive MGO films have broad application prospects in the fields of smart actuators, sensing devices, and biology and health care.