Heat is stubborn. Unlike light or sound, it does not travel in clear beams or waves that engineers can bend, focus, or hide with compact devices. Instead, heat spreads out slowly and relentlessly by diffusion, blurring temperature patterns as it moves.
That makes it hard to control how objects appear to heat-sensing cameras or how they interact with their thermal surroundings. Until now, the only reliable ways to manage heat have involved thick insulation, bulky heat spreaders, or large passive structures.
A new study shows a way around this problem. The study authors have demonstrated a device that makes a small object disturb heat flow as strongly as an object nine times larger in radius—without changing the object itself.
By actively injecting and removing heat along a carefully designed boundary, the system forces heat to flow around the object as if it were much bigger than it really is. The result is a compact object leaving a thermal footprint far larger than its physical size. Scientists call this thermal superscattering,
“This approach enables thermal signature manipulation beyond physical size constraints, with potential applications in thermal superabsorbers/supersources, thermal camouflage, and energy management,” the study authors note.
Why has heat been so hard to manipulate
Engineers already know how to steer steady heat flow using patterned materials, an area known as thermotics. A powerful branch of this field, transformation thermotics, borrows mathematical tools from physics to reshape how heat diffuses through space.
Instead of redesigning an object, scientists redesign the pathways that heat follows around it. If done correctly, the temperature pattern outside a shell can be made to match that of a completely different, virtual object with another size or shape.
However, the problem appears when researchers try to push this idea to extremes. To make a small object behave like a much larger one, the mathematics demands part of the surrounding shell to have negative thermal conductivity.
Such a material would drive heat from colder regions to hotter ones without external energy— something that simply cannot exist as a passive material (heat flows from warmer to colder regions, a basic rule of thermodynamics). This single requirement has blocked real-world demonstrations of thermal superscattering for years.
Using three boundaries to solve the problem
The new study abandons the idea of a purely passive shell. Instead, the researchers replace the impossible material with an active thermal metasurface—a boundary lined with controllable heating and cooling elements.
The team began with a reference problem. In this ideal scenario, a large object with thermal conductivity κₐ sits inside a background material with conductivity κ_b. This large object strongly distorts the surrounding temperature field.
The researchers then designed a much smaller physical object, wrapped in a shell, and used a mathematical coordinate transformation to link the two situations. The goal was to make the temperature and heat flow outside a chosen boundary identical in both cases.
This transformation ties three boundaries together: the inner object boundary ρ₁(θ), the shell boundary ρ₂(θ), and the outer “virtual” boundary ρ₃(θ), which represents the apparent size of the enlarged object. These are linked by a simple relation: ρ₁ρ₃ = ρ₂².
When the equations are worked through, they show that the shell generally needs to conduct heat differently in different directions and vary from place to place. More importantly, the region responsible for superscattering ends up with an effective negative thermal conductivity.
Rather than trying to build that impossible shell, the researchers kept a normal, positive-conductivity shell and added an active boundary. Along this boundary, they imposed a carefully calculated heat-flux pattern.
In simple terms, the boundary elements either inject heat or pull it out, supplying exactly the missing behavior that the negative material would have provided. Mathematically, the required boundary heat source qₛ is related to the normal heat flux qₙ by qₛ = −2qₙ, using a defined sign convention.
As these boundary elements consume electrical power, they do not violate thermodynamics. They act as tiny, distributed heat pumps rather than as a passive material that defies physical laws.
From equations to a working device
To demonstrate the idea experimentally, the team focused on a simple, circular geometry and a super-insulating case, where the virtual object blocks heat flow entirely.
The setup used a copper sheet as the background material. Water baths fixed the ends of the sheet at 320 K and 287 K, creating a steady temperature gradient. At the center sat a small insulated disk with a radius of just 10 mm.
Around it, at a radius of 30 mm, the researchers placed a ring of 10 thermoelectric modules. These devices can heat or cool depending on the direction of the electrical current, making them ideal for active control.
Each module covered a 36° segment of the ring, approximating the continuous boundary predicted by theory. After allowing the system to settle for about 30 seconds, the team measured the surface temperature using an infrared camera.
For comparison, they examined four cases: a uniform copper sheet, a small insulated region alone, a large insulated region with a 90 mm radius, and the small insulated region paired with the active ring.
The result was super impressive. When the ring was driven with the calculated heat-flux pattern, the measured temperature field closely matched that of the much larger insulated region.
“Experimental validation shows the fabricated superscatterer amplifies the thermal scattering signature of a small insulated circular region by nine times, effectively mimicking the scattering signature of a circular region with ninefold radius,” the study authors said.
Computer simulations supported the measurements and showed that the same approach can work for non-circular shapes as well, as long as the boundary control follows the transformation rules.
A practical thermal superscattering approach
This work changes what is possible in steady-state heat control. By replacing impossible materials with active thermal metasurfaces, the researchers have opened a practical route to thermal superscattering and thermal illusions.
In principle, the approach could help reshape thermal signatures for infrared camouflage, improve thermal management in compact electronics, or guide heat flow in energy-harvesting systems.
Next, the researchers aim to improve efficiency, explore more complex shapes, and extend the concept to broader thermal scenarios.
The study is published in the journal Advanced Science.