Researchers from China's Zhejiang University claim to have developed a drone with a sci-fi-esque cloaking device that makes it entirely invisible during flight whether it's in the air, on the ground, or even against the moving backdrop of the sea — to electromagnetic sensors, at least.
"Decades ago, the advent of metamaterials and transformation optics sparked considerable interest in invisibility cloaks, which have been mainly demonstrated in ground and waveguide modalities. However, an omnidirectional flying cloak has not been achieved, primarily due to the challenges associated with dynamic synthesis of metasurface dispersion," the researchers claim in the abstract to their paper. "We demonstrate an autonomous aeroamphibious invisibility cloak that incorporates a suite of perception, decision, and execution modules, capable of maintaining invisibility amidst kaleidoscopic backgrounds and neutralizing external stimuli."
Key to the drone's success in hiding is its on-board processing system. Powered by an NVIDIA Jetson Xavier NX, the drone includes three core sensors: an electromagnetic (EM) radiation detector, a visible-light camera, and a gyroscope. Data from these are fed into a generation-eliminination TensorFlow model, which then controls reconfigurable metasurfaces on the outside of the drone through an STMicroelectronics STM32F103 microcontroller and an RS485 serial bus.
"According to the output," the researchers say, "the reconfigurable spatiotemporal metasurface veneers globally manipulate the scattering wave by directly controlling the temporal sequence of each meta-atom. As a consequence, when freely shuttling among sea, land, and air, the drone can maintain invisibility at all times or disguise itself into other illusive scattering appearances."
While the drone can make itself invisible to electromagnetic sensors, it's somewhat easy to spot with the naked eye. (📷: Qian et al)
To prove the concept, the team flew the drone across three radar receivers in both cloaked and uncloaked modes. When uncloaked, the radar receivers quickly picked up the presence of an unexpected object as the drone passed over the test zone; when cloaked, the sensors were unable to distinguish it from background noise. In both cases, though, the drone was easily visible to the naked eye.
The team's work has been published in the journal Advanced Photonics under open-access terms.
