Tough, Self-Healing, Strain-Sensitive MXene/Ni Hydrogel for Electromagnetic Shielding and Wearable Sensors

Existing electromagnetic shielding materials often suffer from issues such as high reflectivity, limited adaptability, and a lack of self-healing capabilities when they are applied. This study investigates electromagnetic shielding materials (MNWPA or MNPPA) developed by integrating MXene (Ti3C2Tx), magnetic nickel nanowires (Ni NWs), or Ni nanoparticles (Ni NPs) into a dual network hydrogel of poly(vinyl alcohol) and poly(acrylic acid). This unique network structure imparts excellent self-healing capabilities to the materials through reversible dynamic covalent, ionic, and hydrogen bonds. This grants the hydrogel robust mechanical properties even after undergoing self-healing within 1 h of damage. The incorporation of MXene and Ni not only enhances conductivity but also achieves favorable impedance matching, resulting in effective electromagnetic interference (EMI) shielding properties for the hydrogel. Notably, the observed shielding mechanism is primarily based on absorption. Interestingly, the MNWPA and MNPPA hydrogels exhibit distinct absorption and reflection losses due to the differing morphologies between Ni NW and Ni NPs. Furthermore, after cut-healing treatment, the MNWPA hydrogels show a higher retention rate of EMI shielding effectiveness (EMI SE). Conversely, after undergoing multiple stretching behaviors, the MNPPA hydrogels demonstrate a higher retention rate of EMI SE. These findings further emphasize the impact of the Ni NW and Ni NP morphologies on the EM shielding performances of the hydrogels. Additionally, the MNWPA and MNPPA hydrogels display a sensitive deformation response and can serve as strain sensors to monitor various movements of the human body. Hence, our study offers a valuable reference for exploring composite EM shielding materials incorporating Ni NW or Ni NPs.