Multi-functional electromagnetic wave absorption hydrogel with adjustable absorption frequency

Abstract

Multi-functional electromagnetic wave (EMW) absorption materials are in high demand in the ever-changing application environment of the 5G era. Hydrogels, characterized by their exceptional flexibility, stretchability, and water-induced polarization loss, represent promising candidates for developing multi-functional EMW absorption materials. However, their practical applications are significantly hindered by the single EMW loss mechanism and water evaporation issues. Additionally, the potential for dynamic absorption tunability in hydrogel-based absorbers has yet to be explored. To address these challenges, we developed a multi-functional hydrogel by incorporating graphene oxide (GO) and Fe₃O₄ into a copolymer network. The oxygen-containing groups on GO interact with water, effectively reducing its polarity and optimizing polarization loss, while the incorporation of Fe₃O₄ significantly enhances magnetic loss. Consequently, the GO/Fe₃O₄ hydrogel achieves a minimum reflection loss of −62.97 dB at 10.9 GHz, with an effective absorption bandwidth of 5.89 GHz. Beyond its excellent stretchability (770 %) and strong adhesion to various substrates, the hydrogel also demonstrates self-healing ability under room temperature or photothermal response. Furthermore, surface modification with PDMS enhances its water retention and self-cleaning abilities. Notably, the PDMS-modified GO/Fe₃O₄ hydrogel possesses the capability to dynamically adjust its absorption frequency by tensile strain, with the maximum adjustable frequency reaching 87 % of the measured band. This study presents a feasible method for developing high-efficiency, multi-functional EMW absorption materials.