Super Tough Multifunctional MXene/PAA-CS Double Network Hydrogels with High Mechanical Sensing Properties and Excellent EMI Shielding Performance

Hydrogels present significant potential in flexible materials designed for electromagnetic interference (EMI) shielding, attributed to their soft, stretchable mechanical properties and water-rich porous structures. Unfortunately, EMI shielding hydrogels commonly suffer from low mechanical properties, deficient fracture energy, and low strength, which limit the serviceability of these materials in complex mechanical environments. In this study, the double network strategy is successfully utilized along with the Hofmeister effect to create MXene/PAA (polyacrylic acid)-CS (chitosan) hydrogels and further strengthen and toughen the gel with (NH 4 ) 2 SO 4 solution. The gel exhibits enhanced functionalities such as outstanding stretchability, excellent strain sensitivity (11.66), and super fracture energy (≥9 kJ m −2 ). Notably, it demonstrates outstanding shielding effectiveness of 73.8 dB in the terahertz (THz) range, and the shielding properties can be effectively tuned by varying the MXene content, the (NH 4 ) 2 SO 4 concentration, and the thickness of the hydrogel. Additionally, the gel shows robust and superior shielding effectiveness after repeated stretching and long-term dehydration. The MXene/PAA-CS double-network (DN) hydrogels would be an excellent candidate for EMI shielding materials in advanced flexible electronic equipment and soft robots.