Biomimetic Water‐Based Metamaterial Absorber for Ultrabroadband Radar Stealth

Abstract Inspired by the hierarchical porous architecture of Pachliopta aristolochiae butterfly wings and leveraging the intrinsic dielectric dispersion of water, it proposes a biomimetic water‐based metamaterial absorber. Breaking conventional compactness‐bandwidth trade‐offs, this work integrates aqueous metamaterials with bio‐inspired architecture, combining butterfly‐derived hierarchical porosity and water's dielectric dispersion to achieve unprecedented microwave absorption. The absorber employs hexagonal water cavities in a polydimethylsiloxane (PDMS) matrix, mimicking butterfly‐wing multiscale pores to extend wave paths through cascaded resonances. Water serves as “artificial melanin,” enabling tunable dielectric loss via molecular relaxation, with absorption dynamically adjusted through water column height/temperature for frequency‐shifting and bandwidth broadening. The centrosymmetric geometry ensures polarization insensitivity and wide‐angle stability. Optimized aqueous unit coupling achieves >95% experimentally verified absorption (17.11–35.74 GHz) and >10 dB simulated radar cross section (RCS) reduction. Experimental validation shows that the measured absorptivity is in high agreement with the simulation results. Unlike rigid multilayered alternatives, this water‐PDMS architecture offers optical transparency, flexibility, and inherent fluidic tunability for functional reconfiguration. With advantages in ultra‐broadband performance, angular stability, and scalable fabrication, the proposed absorber opens new avenues for adaptive camouflage, electromagnetic shielding, and multispectral stealth technologies.