MIT engineers peel back the future of night vision

The technique, which allows the separation of delicate films from their growth substrates, enabled the creation of the thinnest known pyroelectric membrane – a mere 10 nanometres thick – highly responsive to subtle heat and radiation changes across the far-infrared spectrum.

The research, published in Nature, introduces a pathway toward advanced devices such as ultrathin wearable sensors, flexible transistors, compact imaging systems, and lightweight night-vision technology. The new film, which does not require bulky cooling systems, offers far-infrared sensitivity comparable to existing cooled photodetectors, while remaining compact and portable.

“This film considerably reduces weight and cost, making it lightweight, portable, and easier to integrate,” said Xinyuan Zhang, Graduate Student in MIT’s Department of Materials Science and Engineering. “For example, it could be directly worn on glasses.”

Zhang is first author on the paper, co-written with colleagues from MIT, the University of Wisconsin at Madison, and multiple other institutions. The study was led by Jeehwan Kim, Associate Professor of Mechanical Engineering and Materials Science and Engineering at MIT, in collaboration with Professor Chang-Beom Eom at the University of Wisconsin.

The team focused on a material known as PMN-PT, a type of pyroelectric crystal that generates an electrical signal in response to temperature fluctuations. Researchers demonstrated that not only could this material be fabricated at nanoscales, but it could also be lifted cleanly from its substrate without requiring an intermediate graphene layer – a departure from Kim’s established ‘remote epitaxy’ method.

“It worked surprisingly well,” Zhang noted. “We found the peeled film is atomically smooth.”

The key, the researchers discovered, lay in the chemical composition of PMN-PT. In collaboration with Rensselaer Polytechnic Institute, they found that its lead atoms, which possess a strong electron affinity, inhibit electron flow between the film and the substrate. This weak interfacial bonding acts like a molecular-scale release agent, enabling the film to be peeled without damaging its crystalline structure.

Armed with this insight, the team fabricated a chip populated with 100 heat-sensing pixels, each measuring 60 square microns. When subjected to tiny changes in temperature, the array showed high sensitivity to far-infrared radiation, opening the door to potential applications in lightweight night-vision systems.

Unlike current night-vision goggles that rely on photodetectors requiring cryogenic cooling to minimise noise, the new pyroelectric films operate at room temperature. This removes the need for cumbersome cooling elements and offers a route to significantly lighter and more compact vision systems for defence and automotive markets.

The research team found that the film responded across the entire infrared spectrum, surpassing the performance window of current systems. This broadband sensitivity could support real-time imaging in autonomous vehicles, allowing them to identify hazards in darkness or poor weather. Other uses could include portable environmental monitors for pollutant detection, or thermal monitors for electronics, helping detect early signs of malfunction in semiconductor chips.

The researchers also believe the lift-off technique can be applied to other materials that lack intrinsic peelability. By infusing a substrate with lead-like atoms, it may be possible to replicate the same easy-separation mechanism across a wider range of electronic materials.

“We envision that our ultrathin films could be made into high-performance night-vision goggles, considering its broad-spectrum infrared sensitivity at room-temperature, which allows for a lightweight design without a cooling system,” Zhang said. “To turn this into a night-vision system, a functional device array should be integrated with readout circuitry. Furthermore, testing in varied environmental conditions is essential for practical applications.”

The research was supported by the US Air Force Office of Scientific Research.