Thermoresistive Network in Phase-Transition Hydrogel: Achieving on/off Switchable Electromagnetic Interference Shielding

Intelligent electromagnetic interference (EMI) shielding materials, with their tunable EM wave response characteristics, have attracted much attention. However, the molecular-level response mechanism is under-explored and the tuning range is narrow. This study proposes an EMI shielding switch hydrogel based on molecular precision manipulation of a thermoresistive network capable of adaptively regulating electromagnetic shielding performance. It has two temperature-controlled switching states: on/off and strong/weak shielding. The hydrogel consists of interpenetrating polyvinyl alcohol (PVA) and poly(N-isopropylacrylamide) (PNIPAM) networks, giving it thermal shrinkable properties. A temperature-induced high contact resistance MXene-carbon nanotubes (MXene-CNTs) conductive network is assembled within it. This combination enables the hydrogel to have switchable EMI shielding performance in the X-band, with a range of 9.3-53.9 dB at different temperatures or thicknesses. The remarkable performance results from the synergistic effect of a temperature-driven shrinkage matrix and a thermoresistive network, involving adjustments of conductive particle stacking, hydrogel conductivity, and electromagnetic wave transmission path. MXenes offer remote-controlled photothermal-responsive on/off switchable EMI shielding. Significantly, the hydrogel's self-healing properties allow it to endure damage and its EMI shielding performance can be quickly restored. This work paves a new way for the rational design of adaptive EMI shielding devices at the molecular level.