Anisotropic variable negative-Poisson-ratio metamaterials for tunable multispectral camouflage and electromagnetic energy harvesting

Abstract

Adaptive electromagnetic compatibility, camouflage, and energy conversion raises challenge in the swiftly responsive modulation. Herein, we designed pixelated negative-Poisson-ratio metamaterials that enable fast control over structural anisotropy and thus electromagnetic properties. One-dimensional conductors are highly oriented in each pixel through sequential shear, stretch, and alignment processes. The uniaxial anisotropy leads to the highest conductive ratio of 2.8 × 10 6 among different directions. This enables the angle-dependent electromagnetic compatibility across transparency–absorption–shielding regions. The meta-framework realizes strain-reliant anisotropic tunability. The deformation continuously adjusts electromagnetic wave absorbance from 0.2 to 0.9 (reflection loss from −0.8 to −17 decibels). Through chess-like assembly, the framework can also maintain deformation-insensitive absorbance beyond 0.9. The proof-of-concept devices harvest environmental electromagnetic energy to electricity. The generator outputs more than 0.5 volts and the cell generate a peak power of 0.75 milliwatt. Besides, the devices demonstrate tunable camouflage in microwave, infrared, and visible spectra.