Waxberry-inspired aerogel metamaterial with gradient pore structure for superior electromagnetic wave absorption

Lightweight porous aerogels have demonstrated efficient electromagnetic wave absorption performance. Nevertheless, the inherent trade-off between favorable impedance matching at the atmosphere-aerogel interface and strong electromagnetic loss within the aerogel matrix has limited the further improvement of the aerogel's electromagnetic wave absorption performance. In this study, a waxberry-inspired gradient-porous aerogel metamaterial (WGAM) was successfully fabricated via an innovative dot-matrix cooling source ice templating technique. The influences of diverse pore structures and repeating unit sizes on the performance of aerogels were systematically investigated and analyzed. The results reveal that the gradient pore structure in WGAM effectively balances the conflict between interface impedance matching and intrinsic electromagnetic loss, enabling WGAM to achieve an ultrabroad effective absorption bandwidth of 12.3 GHz within the range of 2–18 GHz. Meanwhile, owing to the 3D radial distribution of internal pores, WGAM retains robust electromagnetic wave absorption capacity even when the incident angle of electromagnetic waves is increased from 5° to 30°. Furthermore, WGAM exhibits favorable mechanical, thermal-insulating, and flame-retardant properties, rendering it a promising candidate for electromagnetic protection applications under complex and harsh environmental conditions.