Ultrathin Electromagnetic–Acoustic Amphibious Stealth Coats

Abstract

Radar and sonar technologies are generally used to detect objects in air space and water. In some cases, both technologies are involved in probing waterborne objects like submarines. However, the simultaneous stealth regarding these two detection methods is not well explored due to the difficulty in satisfying material properties for two different physical systems. In this work, an artificial ultrathin amphibious stealth coat with a minimum thickness less than 0.5 mm achieving free‐space microwave and underwater acoustic absorption is proposed and demonstrated. It is realized by combining an electromagnetic metasurface and an acoustic metasurface—a flexible printed circuit with multisized metal resonators and a polydimethylsiloxane film with multisized air cavities. These two alien metasurfaces are engineered with minimized disturbance to each other by controlling the thicknesses of the resonators as thin as possible. A free‐space microwave absorptivity over 80% in the 12.38–13.7 GHz region and an underwater acoustic reflectance less than 10% in the 80–160 kHz region are obtained experimentally. The current work may shed light on advanced stealth technologies of the free‐space microwaves and underwater acoustic waves.

Coupled Solid and Inverse Antenna Stacks Above Metal Ground as Metamaterial Perfect Electromagnetic Wave Absorbers with Extreme Subwavelength Thicknesses

“…Subwavelength electromagnetic (EM) wave absorbers are of substantial interest across all parts of the EM spectrum, [1][2][3][4][5] but are especially important for the MHz and GHz regimes due to their practical significance in stealth technology, [6,7] heat detection, [8] sensing, [9] and communication. [10] EM wave absorbers are particularly important for self-driving vehicles or aerial systems, where insufficient protection against stray EM signals may lead to an electronic malfunction, posing a serious risk to human safety.…”

Thin Multispectral Camouflage Absorber Based on Metasurfaces with Wide Infrared Radiative Cooling Window

“…[1][2][3] With regard to the active working mode of microwave detectors, the radar camouflage materials possess high absorptivity and low reflectivity. [4][5][6][7][8] On the contrary, to evade the detection of infrared detectors, the infrared camouflage materials equipped with low infrared emissivity, which means low absorptivity and high reflectivity, are demanded IR Herein, a hierarchical metamaterial (HMM) is reported to achieve multispectral camouflage for thermal infrared detectors and radar. The HMM consists of a frequency-selective emitter (FSE) integrated with a microwave absorber (MA).…”

“…[ 1–3 ] With regard to the active working mode of microwave detectors, the radar camouflage materials possess high absorptivity and low reflectivity. [ 4–8 ] On the contrary, to evade the detection of infrared detectors, the infrared camouflage materials equipped with low infrared emissivity, which means low absorptivity and high reflectivity, are demanded IR stealth according to Kirchhoff's law. [ 9–12 ] Another important point is that the infrared with 5–8 μm wavelength cannot pass the atmosphere.…”

Invisibility Cloak Technology of Anti-Infrared Detection Materials Prepared Using CoGaZnSe Multilayer Nanofilms

“…At present, the research of infrared stealth materials has been expanded to the nanoscale level such as multidoped nanomaterials and nanometal materials. The research of stealth technology using different materials mainly focuses on the three aspects, including the characteristics of infrared radiation change, , the intensity of infrared radiation reduction, , and spectral conversion. , However, these studies still face some limitations to be overcome with respect to complex preparation processes, narrow spectral ranges, and poor antidetection efficiency.…”