Polyvinyl alcohol /chitosan biomimetic hydrogel enhanced by MXene for excellent electromagnetic shielding and pressure sensing.

Traditional electromagnetic shielding materials are difficult to realize practical applications due to excessive fillers, poor mechanical properties, and difficulty in preservation, etc. Hydrogel is a biomaterial with good biocompatibility and sustainability, which not only can overcome the aforementioned issues, but its biomimetic hierarchical porous structure also enables multifunctional applications. In this paper, a honeycomb-like unidirectional porous wall structured hydrogel is prepared by a simple freeze-thaw cycle and salting out method. Polyvinyl alcohol (PVA) and chitosan (CS) form a double cross-linked network (DN) enhanced by MXene, resulting in excellent mechanical and flexibility. Due to the synergistic effects of MXene, water, FeO, abundant interfaces and micrometer porous wall structure, the electromagnetic shielding performance is enhanced. EMI SE increases by 30.7 dB as the MXene concentration increases from 0 to 1.5 wt%, and EMI SE increases from 7.9 to 66.7 dB as the water content increases from 0 to 76 %. Besides this, we encapsulate the hydrogel into a simple sensor, the signal response is rapid, the response /recovery time is 50/100 ms respectively, and it exhibits good sensitivity (0.0187 kPa). Different signals are generated based on variations in pressure, which holds significant importance for the development of wearable flexible sensors and information encoding.