Poly(vinyl alcohol)\nHydrogels Enhanced with Ti<sub>3</sub>C<sub>2</sub>T<sub><i>x</i></sub> MXene Nanosheets\nand Aramid Nanofibers for Electromagnetic Shielding and Motion Detection

The progress in electronic devices has led to more electromagnetic\npollution. The importance of green and stable electromagnetic shielding\ndevices cannot be overstated. Here, a PVA hydrogel reinforced by MXene\nand aramid nanofibers (ANFs) is prepared through solution exchange,\nfreeze–thaw cycles, and the process of salting out. The unidirectional\nporous wall structure, combined with a water-rich environment connecting\nthe MXene-dominated conductive network, and the rich interfaces endow\nthe hydrogel with excellent EMI SE in the X-band at extremely low\nfiller concentrations (1.5 wt %), reaching up to 64.5 dB. We determine\nthe effect of MXene and water on the electromagnetic shielding effect\nby adjusting the content of MXene and water. The EMI SE of the 3 mm\nhydrogel increases by 33.4 dB when the MXene concentration augments\nfrom 0 to 1.5 wt %. Similarly, when the water content of hydrogels\naugments from 0 to 95 wt %, their EMI SE augments from 7.86 to 52\ndB. In addition, the hydrogel exhibits excellent pressure sensing\nperformance, capable of detecting motion with response and recovery\ntimes of 210 and 110 ms, respectively, and an optimal sensitivity\nof 0.308 kPa<sup>–1</sup>. It can also encode and encrypt information\nbased on different signals, presenting profound prospects for smart\nsensing and wearable devices.