Rapid Water-Responsive Shape-Memory Nanocellulose/MXene Aerogel for Piezoresistive Sensing and Electromagnetic Interference Shielding in Underwater Environments

In recent years, the development of flexible wearable materials and electromagnetic shielding materials has progressed rapidly. The demand for monitoring movement data and providing protection against electromagnetic waves has also increased significantly. However, there is currently a lack of materials suitable for applications in high-humidity and underwater environments, which limits their ability to meet the needs of users in special conditions. In this study, we designed an aerogel sensor based on MXene and bacterial cellulose (BC) capable of monitoring movement in both dry and wet states while also exhibiting good electromagnetic wave absorption properties.The sensor showed a sensitivity of −6.43 with excellent linearity (99.8%) and stability. The sensor exhibits a high compressive strength of up to 15 kPa in the dry state, with a resistance change rate reaching 50% under 8% strain, and can undergo 710 cycles, demonstrating high sensitivity and stability. Under water-induced conditions, the sensor demonstrates high flexibility, shape-memory performance, and a wide strain range (0–80%) as a wet-state sensor, maintaining good structural stability and sensing performance throughout the dry–wet transition process. The BCNF/MXene sensor also demonstrates good resistance to electromagnetic interference. The RLmin of the BCNF/MXene-30% sensor reaches −45.60 dB, with an electromagnetic wave absorption rate of 99.99% and a relatively broad effective absorption bandwidth (4 GHz). This resistive sensor can be applied in electronic skins, human–machine interactions, smart wearable devices, and personalized health monitoring. Our work successfully demonstrated the application of water-sensitive shape-memory materials in electronic skins, health monitoring components, and electromagnetic wave protection.