Designing a flexible material to protect buildings, military personnel  May 27, 2020 Cloaking materials are mature because the properties of acoustic (radar, sonar) and optical waves (infrared) are well-understood. However, cloaking for elastic waves in solid media is lagging. A team of researchers in the US (University of Missouri, MIT) has designed and fabricated a new class of cloaking materials which is composed of a functionally graded lattice embedded in an isotropic continuum background. The layers were 3-D printed and manually assembled. They experimentally and numerically investigated the characteristics of the proposed cloak and found very good cloaking performance under both tension and shear loadings. Potential applications for […]

Camouflage made of quantum material could hide you from infrared cameras  December 17, 2019 For most solids, the thermally emitted power increases monotonically with temperature in a one-to-one relationship that enables applications such as infrared imaging and noncontact thermometry. A team of researchers in the US (University of Wisconsin, Harvard University, Purdue University, MIT, Brookhaven National Laboratory) has shown that ultrathin samarium nickel oxide undergoes a fully reversible, temperature-driven solid-state phase transition. Its smooth transition enabled them to engineer the temperature dependence of emissivity to precisely cancel out the intrinsic blackbody profile for both heating and cooling. The design results in temperature-independent thermally emitted power within the long-wave atmospheric transparency […]

Sound-redirecting prototype could fool eavesdroppers  November 12, 2019 Though the idea of engineering materials or surfaces to strategically refract sound waves is well-established, most existing designs are static. An international team of researchers (China, University of Nebraska) has designed a tunable metasurface with Helmholtz resonance. Moving sliders in the design allow full phase shift with a high transmission ratio in a broad frequency bandwidth. The design can be used for tunable wave front redirection, focusing with varying wavelengths and sound source illusion, as shown in numerical and experimental examples. The technique may be used in applications that range from magnifying signals to disorienting adversaries…read […]

Study opens a new route to achieving invisibility without using metamaterials  April 23, 2019 Researchers in Japan report a way of making a cylinder invisible without a cloak for monochromatic illumination at optical frequency including those visible to the human eye. Based on Mie scattering they looked for a region indicating very low scattering efficiency, which they knew would correspond to the cylinder’s invisibility and determined that in this region invisibility would occur when the refractive index of the cylinder ranges from 2.7 to 3.8. Natural materials such as silicon, aluminum arsenide and germanium arsenide, which are commonly used in semiconductor technology fall in this category. They found that the […]

A direct current (DC) remote cloak to hide arbitrary objects  March 27, 2019 An international team of researchers (China, Singapore) used a negative resistor network with active elements to achieve the remote function of the DC cloak. Based on this network, the cloak can remotely generate a hidden region without distorting the currents far from the cloaked region. The experimental results show that any object in the hidden region is invisible to a DC detector. The cloak does not require any knowledge of the hidden object. The cloaking device may find potential applications in medical or geologic research…read more. Open Access TECHNICAL ARTICLE

New technique to make objects invisible proposed

Eurekalert  November 26, 2018 Most of the techniques for cloaking harness the extraordinary properties of certain materials to make light circumvent the object to be made invisible. An international team of researchers (Spain, Italy) has developed a technique using the electromagnetic properties of specific materials which can make certain objects invisible when they are introduced as fillers. This plasmonic cloaking makes the object and the filler jointly invisible. The method makes it possible to achieve invisibility from the interior of an object without using any external device and allows the object to interact with its environment without being hampered by […]

Spectral cloaking could make objects invisible under realistic conditions  June 28, 2018 Most current cloaking devices can fully conceal the object of interest only when the object is illuminated with just one color of light. Researchers in Canada propose a new conceptual approach enabling the realization of full-field broadband invisibility. This involves a customized and reversible redistribution of the illumination frequency content, allowing the wave to propagate through the object of interest while preventing any interaction between the wave and the object. They demonstrated the concealment of a broadband optical filter from detection with a phase-coherent light pulse of 500 GHz bandwidth, showing full restoration of the complex […]

Cloaking devices — it’s not just ‘Star Trek’ anymore

Eurekalert   May 10, 2018 Researchers at Pennsylvania State University have designed material to redirect approaching waves around an object without scattering the wave energy, concealing the object from the sound waves. They designed a 3-foot-tall pyramid out of perforated steel plates and placed the structure on the floor of a large underwater research tank. Inside the tank, a source hydrophone produced acoustic waves between 7,000 Hz and 12,000 Hz, several receiver hydrophones around the tank monitoring reflected acoustic waves. The wave reflected from the metamaterial matched the phase of the reflected wave from the surface demonstrating that the material could […]