Backyard insect inspires invisibility devices, next gen tech

Phys.org  March 18, 2024 The leafhoppers cover their body surfaces with brochosomes, buckyball-shaped, nanoscopic spheroids with through-holes distributed across their surfaces, representing a class of deployable optical materials that are rare in nature. A team of researchers in the US (University of Pennsylvania, Carnegie Mellon University) investigated the optical form-to-function relationship of brochosomes and demonstrated that the hierarchical geometries of brochosomes are engineered within a narrow size range with through-hole architecture to significantly reduce light reflection. They showed that the diameters of brochosomes are engineered to maximize broadband light scattering, while the secondary through-holes are designed to function as short-wavelength, […]

Whole-infrared-band camouflage with dual-band radiative heat dissipation

Phys.org  February 7, 2024 Achieving effective camouflage and thermal management across the entire infrared spectrum, especially the short-wave infrared (SWIR) band, remains challenging. Researchers in China proposed a multilayer wavelength-selective emitter that achieves effective camouflage across the entire infrared spectrum, including the near-infrared (NIR), SWIR, mid-wave infrared (MWIR), and long-wave infrared (LWIR) bands, as well as the visible (VIS) band. The emitter would enable radiative heat dissipation in two non-atmospheric windows. The emitter’s properties were characterized by low emittance in the SWIR/MWIR/LWIR bands, and low reflectance in the VIS/NIR bands. The high emittance in the two non-atmospheric windows would ensure […]

Source-shifting metastructures composed of only one resin for location camouflaging

Science Daily  May 30, 2023 Researchers in Japan numerically demonstrated an inverse design of a structure for camouflaging the location of a sound source as if the sound emanated from a different location. They used a topology optimization approach used in acoustic elastic coupled problems, the difference between the sound pressure fields emanating from an actual source and a virtual source, was the objective function infimized in camouflaging the sound source. Optimal topologies of elastic structures made of acrylonitrile butadiene styrene were designed for the camouflaging purpose, acoustic metamaterials were not used. The metastructures (source-shifters) were expressed at the design […]

Acoustics researchers develop novel underwater carpet cloak

Phys.org  July 28, 2022 Aided by a reflecting surface, the acoustic carpet cloak has become one of the most practically feasible invisibility devices. However, due to the difficulty in the realization of ideal material parameters, the underwater carpet cloaks could only work for a small incident angle. Researchers in China designed an underwater carpet cloak using a three-component metafluid composed of syntactic foam, steel, and water. The syntactic foam, which is synthesized from epoxy resin and hollow glass microspheres, exhibits lower mass density and higher sound velocity relative to water. By periodically embedding the syntactic foam and steel rods in […]

Rubbery camouflage skin exhibits smart and stretchy behaviors

EureakAlert  June 13, 2022 Cephalopod (octopuses, squids, and cuttlefish) skin is a soft organ that can endure complex deformations, such as expanding, contracting, bending, and twisting, capable of cognitive sensing and responding that enable the skin to sense light, react and camouflage its wearer. While artificial skins with either these physical or these cognitive capabilities have existed, none has simultaneously exhibited both qualities. An international team of researchers (USA – Pennsylvania State University, University of Houston, South Korea, China) has developed artificial neuromorphic cognitive skins based on arrayed, biaxially stretchable synaptic transistors constructed entirely out of elastomeric materials. Through investigation […]

Form-free metasurfaces enable novel and intelligent optical illusion

Nanowerk  March 4, 2022 The mainstream transformation-optics-based optical illusions are inherently hindered by the extreme requirements of metamaterial compositions in practice and large computational cost. To address these issues researchers in China have proposed an intelligent optical illusion supported by form-free metasurfaces via a deep learning architecture which can render a similar illusion effect and greatly reduce the parameter space in physics. They have presented illustrative examples of conformal metasurfaces with a high-fidelity inverse design from either the near- or far-field in the simulation and experiment. They developed a full set of intelligent systems to benchmark the real-world optical illusion […]

Engineering a polymer network to act as active camouflage on demand

Phys.org  September 16, 2021 Despite extensive efforts to create colour-changing materials and devices, it is challenging to achieve pixelated structural coloration with broadband spectral shifts in a compact space. An international team of researchers (USA – University of Pennsylvania, South Korea) describes pneumatically inflating thin membranes of main-chain chiral nematic liquid crystalline elastomers that have such properties. By taking advantage of the large elasticity anisotropy and Poisson’s ratio (>0.5) of these materials, they geometrically programed the size and the layout of the encapsulated air channels to achieve colour shifting from near-infrared to ultraviolet wavelengths with less than 20% equi-biaxial transverse […]

Active camouflage artificial skin in visible-to-infrared range

Phys.org  December 2, 2020 Researchers in South Korea have developed a multispectral imperceptible skin that enables human skin to actively blend into the background both in the IR‐visible integrated spectrum only by simple temperature control with active cooling and heating. The thermochromic layer on the outer surface of the device, which produces various colors based on device surface temperature, expands the cloaking range to the visible spectrum and ultimately completes day‐and‐night stealth platform simply by controlling device temperature. In addition, the scalable pixelization of the device allows localized control of each autonomous pixel, enabling the artificial skin surface to adapt […]

Asymmetric optical camouflage: Tunable reflective color accompanied by optical Janus effect

Phys.org  October 20, 2020 Going beyond an improved colour gamut, an asymmetric colour contrast, which depends on the viewing direction, and its ability to readily deliver information could create opportunities for a wide range of applications, such as next-generation optical switches, colour displays, and security features in anti-counterfeiting devices. Researchers in South Korea propose a simple Fabry–Perot etalon architecture capable of generating viewing-direction-sensitive colour contrasts and encrypting pre-inscribed information upon immersion in particular solvents. Based on the experimental verification of the theoretical modelling, they have discovered a completely new and exotic optical phenomenon involving a tunable colour switch for viewing-direction-dependent […]

Researchers create surface coating that can create false infrared images

UC Berkeley  July 23, 2020 At certain temperature tungsten-doped vanadium dioxide can phase shift from an insulator to a metal. An international team of researchers (US Berkeley, Singapore, China) created special structures made from delicately engineered thin films of tungsten-doped vanadium dioxide. With judicious engineering of the doping profile, the insulator-metal phase transition can even out, allowing the substance to emit a constant level of thermal radiation over wide range of temperature variations (15-70 degrees Celsius). This state of equilibrium prevents a camera from detecting the true infrared signals that an object normally emits around room temperature. The coatings can […]