Intelligent Hydrogels Enabled Large-Scale Variability in Continuously Tunable Microwave Absorption

Abstract

Intelligent materials with tunable microwave absorption are crucial for addressing challenges in complex electromagnetic environments. A significant challenge in this field is achieving large, continuous, and precise control over microwave absorption properties. To address these issues, a series of intelligent hydrogels are directly fabricated by the dynamic interaction of natural polyphenols and graphene oxide, which enabled large-scale variability in continuously tunable microwave absorption with temperature change. This tunability is attributed to the dynamic interplay between π–π stacking and hydrogen bonding at different temperatures. At elevated temperatures, π–π stacking can boost the electron transfer, impedance matching, and electromagnetic loss capacity. Notably, the hydrogels demonstrate a near-linear change up to 88.7% in dielectric constant over the 20–80 °C range, achieving a maximum reflection loss difference of 43.99 dB and an effective absorption bandwidth difference of 3.08 GHz. Furthermore, the hydrogels also exhibit excellent tunability and switching function in wireless charging tests, near-field scanning, wireless image communication, and Radar Cross Section (RCS) simulations of aircraft.