Flexible ultrabroadband metamaterial absorber

The gradient serpentine unit cell of the MAs provides mechanical stretchability and a graded impedance profile minimizing reflection across a wide frequency range, while the Ni filler provides a three-dimensional conductive network enabling both dielectric and magnetic loss mechanisms, as revealed by the results of electromagnetic parameter measurements at 2–18 GHz.

The best balance between impedance matching and energy dissipation is achieved using a full-wave simulation–optimized gradient serpentine geometry and a Ni loading of 60 wt%. The corresponding MA exhibits an exceptional absorption bandwidth (3.2–40 GHz), polarization-insensitive behavior, wide-angle stability (incidence angle = 0°–65°), and outstanding mechanical flexibility, withstanding tensile strains of >200% without structural failure.