A Biomimetic Double Water Meta‐Atom Lattice for Ultra‐Broadband Multi‐Gradient Microwave Absorption

ABSTRACT Water‐based metamaterial absorbers have demonstrated promising broadband absorption capabilities. However, their performance at lower frequencies, particularly in the S and C bands, remains limited due to impedance mismatch and low loss factors. Herein, inspired by the anti‐reflective microstructure of moth eyes, we propose a dual‐phase optimization strategy to develop a multilayered gradient absorber. This approach employs a double meta‐atom lattice of conical water units with their geometry refined by a genetic algorithm to enhance impedance matching and energy dissipation. The resulting water‐based absorber achieves an ultra‐broadband of 3.1–25.1 GHz, fully covering the C, X, and Ku bands, along with partial coverage of the S and K bands, superior to the advanced water‐based absorber at such low frequencies. Systematic analysis of impedance matching, reflection losses of different structures and power loss distribution reveals that the broadband absorption arises from synergistic inter‐layer and inter‐meta‐atom resonances as well as multiple reflections between structures. This study provides a low‐cost and scalable strategy for preparing high‐performance ultra‐wideband absorbers, with significant potential applications in electromagnetic stealth and protection.