Active microwave absorbers with self-supervised adaptive frequency regulation and optical transparency are of great significance for applications such as self-adapting electromagnetic stealth and energy harvesting for satellites or unmanned aerial vehicles. Conventional active microwave-absorbing materials and devices typically suffer from bulky volume, require complicated distributed circuit components, and are optically opaque, which significantly hinders their practicality in increasingly complex electromagnetic environments. In this context, M. Geng et al. reported experimentally an optically transparent cognitive metasurface system made of patterned graphene sandwich structures, a radio frequency sensor array, and a microcontroller unit. The frequency signal of the incident electromagnetic wave detected by the sensor array is transmitted to the microcontroller unit returning a precise control of the bias voltage applied on graphene, which results in the adaptive adjustment of the metasurface’s optimal absorption frequency to match the incident electromagnetic wave. The whole absorber system is a closed-loop without any human intervention. This work is a significant step from active metasurfaces to intelligent meta-devices and may promote the development of other adaptive and intelligent meta-devices and meta-systems with high-level recognition and manipulation.

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