Background
With the rapid development of 5G/6G communications and the Internet of Things, electromagnetic interference (EMI) and radiation pollution are increasingly affecting device performance, information security, and potentially pose risks to human health. Meanwhile, aerospace and defense applications demand EMI shielding materials capable of ultra-broadband regulation spanning from the microwave to the terahertz and infrared regimes, together with high stretchability, robust mechanical properties, environmental stability, and reliable strain-sensing performance in complex environments.
Conductive hydrogels are promising flexible EMI shielding materials due to their intrinsic stretchability. Nevertheless, at low conductive filler contents, it remains challenging to simultaneously achieve high EMI shielding effectiveness and robust mechanical performance. Although increasing filler contents can effectively enhance EMI shielding effectiveness, it often leads to compromised extensibility and toughness, together with substantially increased material cost. Moreover, existing studies are predominantly confined to the microwave regime, whereas systematic investigations in the terahertz and infrared ranges remain limited. In addition, the water-rich polymeric matrix renders hydrogels vulnerable to environmental instability and degraded of shielding performance under tensile deformation. Consequently, developing multifunctional hydrogel systems that integrate low filler content, broadband electromagnetic shielding, infrared stealth, mechanical robustness, and environmental stability remains a key challenge.

Research Progress
In this work, a synergistic MXene/(NH₄)₂SO₄ treatment strategy is proposed and systematically validated. By combining salt‐out processing based on the Hofmeister effect with a MXene-enabled conductive network, a double‐network MXene-composite hydrogel is fabricated. At an extremely low filler content (0.12 wt%), MNMSPC hydrogel exhibits an approximately threefold improvement in overall mechanical performance, including strength, toughness, and stretchability. Meanwhile, the gel achieves efficient broadband EMI shielding covering the X, Ku, Ka, and terahertz frequency bands, with a maximum shielding effectiveness exceeding 60 dB, together with excellent infrared stealth performance.
To elucidate the electromagnetic shielding mechanisms of the MNSPC double‐network hydrogel, a series of control samples were prepared and their electromagnetic parameters were systematically evaluated across different frequency ranges. The results indicate that the outstanding broadband electromagnetic interference shielding and infrared stealth properties primarily originate from the continuous conductive network formed by MXene, which provides high electrical conductivity and dominates reflection and Ohmic loss. The introduction of (NH₄)₂SO₄ further enhances ionic polarization and conduction loss through the presence of mobile ions. In addition, the porous structure of the hydrogel prolongs the propagation path of electromagnetic waves, thereby promoting multiple internal reflections and enhanced absorption.
Furthermore, the hydrogel maintains electromagnetic shielding effectiveness exceeding that of commercial-grade shielding materials, as well as effective infrared stealth functionality, under various harsh conditions including repeated stretching, prolonged water evaporation, low-temperature freezing, high-temperature heating, alcohol lamp flame exposure, and high-strain stretching.

Future Prospects
The developed multifunctional hydrogel with fabricating strategy would be suitable for EMI protection in flexible wearable electronics and soft robotic skins. The strategy also demonstrates distinct advantages for stealth protection in complex electromagnetic environments. Future work will focus on integrating programmable structural designs and external-field-responsive units to enable dynamically tunable and intelligent regulation of electromagnetic shielding and infrared stealth properties. It is anticipated that high-performance flexible EMI regulation platforms integrating sensing, protection, and stealth functionalities can be realized for operation under complex electromagnetic conditions.

The complete study is accessible via DOI:10.34133/research.1020