Metamaterials are carefully engineered materials that possess desirable properties and can be used to manipulate electromagnetic, acoustic, or other types of waves in interesting ways. Some materials scientists and engineers have been trying to use these materials to develop so-called invisible devices, or, in other words, devices that do not disturb the environment around them or reveal their presence to other technologies nearby.
Most proposed approaches for realizing invisible devices entail surrounding devices with a metamaterial shell that prevents scattering. While devices created using these strategies do not disturb their surrounding environment, they still distort what is happening within the metamaterial shell, thus they remain partly visible.
Researchers at Fudan University have introduced a new approach to realize devices that are truly and entirely invisible using metamaterials. Their proposed solution, outlined in a paper published in Physical Review Letters, was found to eliminate scattering effects both outside and inside a metamaterial cloaking shell.
“The inspiration for this work came from a long-standing dilemma in designing metamaterials,” Jiping Huang, Professor at Fudan University and senior author of the paper told Tech Xplore.
“In many cases, metamaterials can be used to remove disturbances in the surrounding environment, but this often creates new disturbances inside the metamaterial itself. In other words, one problem is solved at the price of creating another.
“An invisibility cloak is a good example. It may hide an object from an outside observer, but the physical field of the cloak itself can still be strongly distorted.”
Designing a device that is truly transparent
The primary goal of the recent work by Huang and his colleagues was to develop a device that does not disturb the outside environment, but that also does not disturb the metamaterial shell used to cloak it from its surroundings. Previously proposed cloaking strategies often made the temperature distribution outside devices appear normal, yet they distorted the temperature inside the metamaterial shell.
“We solved this problem in two steps,” explained Huang. “First, we used a conventional design to eliminate the disturbance in the surrounding region. Then we introduced an additional coordinate transformation to correct the temperature distribution inside the shell, so that the temperature lines there also become regular and undisturbed.”
To realize their idea experimentally, the researchers first needed to engineer metamaterials with special anisotropic thermal properties, meaning that heat flows in specific ways inside them. To design the microscopic structures that would yield the desired properties, they used advanced computational tools known as deep learning algorithms.
“After fabricating the samples, we tested them under a temperature gradient and observed the temperature distributions with an infrared camera,” said Huang. “The experiments confirmed that the temperature remains undisturbed both outside the device and inside its shell.”
The design introduced by the researchers was found to achieve true invisibility via a regime known as dual-zero-scattering. This regime is what ultimately eliminates scattering both inside and outside of the metamaterial cloaking shell.
A promising demonstration and possible future applications
Huang and his colleagues were the first to report dual-zero-scattering in a metamaterial-cloaked device. The metamaterial shell they designed was found to effectively eliminate scattering both inside and outside of it, producing a system in which the flow of heat remains entirely undisturbed.
“We realized dual-zero-scattering for the first time, which means that we achieved true transparency in a diffusion system: the device does not disturb either the surrounding environment or its own shell,” said Huang.
“In practical terms, this could help us build thermally transparent sensors—sensors that can measure temperature without disturbing the surrounding temperature field. This is important because ordinary sensors often change the very temperature they are trying to detect.”
The team’s cloaking approach could soon be used to create various invisible devices, including non-invasive thermal sensors, systems that can confine heat in specific regions, high-precision thermal measurement tools, and sensitive superconducting quantum technologies.
Invisible devices will be particularly advantageous in scenarios where minimal disturbance can have undesirable effects, for instance when collecting data inside the human body or to minimize errors in quantum computation.
“We now plan to take this concept beyond just heat,” added Huang. “The mathematical rules governing heat diffusion are very similar to other physical systems. We hope to apply this ‘dual-zero-scattering’ framework to control sound waves, light, and mechanical vibrations.
“We are also exploring how to combine this with more advanced AI to create ‘smart cloaks’ that can adapt themselves to changing environments automatically.”
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Publication details
Anonymous, Dual-zero-scattering in diffusive transport, Physical Review Letters (2026). DOI: 10.1103/vxsz-nnf3
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