Poly(vinyl alcohol) Hydrogels Enhanced with Ti₃C₂T_<i>x</i> MXene Nanosheets and Aramid Nanofibers for Electromagnetic Shielding and Motion Detection

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