CHAMPAIGN, Ill. — Researchers have designed and built the first 3D device that can make objects invisible to heat, an advance that could transform how we protect sensitive electronics, manage heat in microchips and shield equipment from thermal detection.
The new thermal cloak can hide objects of almost any shape from infrared cameras while also protecting them from extreme temperatures. Unlike previous designs, which worked only in two dimensions or from a single direction, the cloak works from essentially any direction. Rather than simply blocking heat, thermal cloaking guides heat around an object so that, to an infrared camera, it appears as if nothing is there.
University of Illinois Urbana-Champaign civil and environmental engineering professor Shelly Zhang , postdoctoral researcher Weichen Li, and graduate student Yibo Wang collaborated with professor Ole Sigmund at the Technical University of Denmark on the study, which is published in the journal Nature Communications.
Click to view a video describing this research
"A real thermal cloak should work no matter where the heat comes from," Zhang said. "Our device can hide a complex 3D object in an infinite number of directions while keeping the temperature inside stable and protected."
Past experiments have only worked in two dimensions or along a single direction of heat flow, far from the ideal of a true 3D cloak. To solve this problem, the team went back to the original theory of transformation thermotics and asked, "What kind of material structure could cover almost all the thermal properties needed for a perfect cloak?"
Their answer was a new type of lattice-based material that can be freely adjusted in three directions. By tuning these dimensions, the researchers can precisely control how well different regions conduct heat. This design covers a much wider range of thermal conductivities than previous approaches — sufficient to closely match the theoretical requirements for ideal cloaking.
The team's thermal cloak is not just a computer model — it has been physically fabricated and tested. The device is a hybrid material, using 3D-printed metal to create a precise aluminum lattice that acts as a high-conductivity material. Mold casting was used to fill in the structure with a rubber-like material with low thermal conductivity.
In the lab, the researchers placed the device between hot and cold regions to create a temperature gradient. Using an infrared camera, they tracked how heat flowed around and through the cloak. From the outside, the temperature field looked as if a object hidden with the cloak was not there at all. Inside the cloaked region, the temperature remained uniform and protected from the external extremes.
To further challenge their design, the team cloaked highly complex 3D geometries, including detailed head-like shapes. They report that no previous experimental thermal cloak comes close to this level of geometric complexity and performance.
The researchers envision wide-ranging applications for this technology, from precisely managing heat around sensitive electronic components to security and defense uses such as helping to hide people or equipment from thermal detection or protecting assets in harsh conditions.
"Any field that needs precise control of heat or needs to protect something from being detected thermally could benefit from this work," Zhang said. "But we also see it more broadly: it's about hiding and protecting information that is carried by heat."
Looking ahead, the team plans to explore smart and multifunctional cloaks. For example, the researchers hope to determine how to mask an object inside the cloak that generates its own heat. This would require a cloak that can concentrate, spread or guide heat on demand within the protected region.
"We've shown that a true 3D omnidirectional thermal cloak is possible," Zhang said. "The next step is to make cloaks that don't just hide and protect, but also actively manipulate heat in useful ways."
The National Science Foundation, the Villum Foundation and the Air Force Office of Scientific Research support this research. Zhang also is affiliated with mechanical science and engineering and the National Center for Supercomputing Applications at Illinois.
