Engineers have created the smallest fully printed infrared light sensors ever made, opening a new path toward cheaper, smaller, and more flexible infrared technologies.
The breakthrough comes from a research team led by Professor Leo Tianshuo Zhao at the University of Hong Kong and could reshape how infrared detectors are built for future electronics.
The study was published in Nature Communications and describes a new nano-printing method that works at room temperature and avoids many of the limits of traditional silicon-based manufacturing.
Infrared, especially near-infrared (NIR) light, plays a key role in modern technology.
It is used in autonomous vehicles to sense surroundings, in medical devices to monitor blood flow and tissues, and in high-speed optical communications.
The problem is that silicon—the backbone of today’s electronics—cannot directly detect near-infrared light. To get around this, manufacturers usually grow special infrared-sensitive materials separately and then attach them to silicon chips. This process is expensive, complex, and makes it hard to shrink devices further.
Professor Zhao’s team took a completely different approach.
Instead of forcing infrared materials to fit into silicon-based systems, they developed a way to print infrared photodetectors directly, using specially designed inks made from tiny particles called colloidal nanocrystals.
Colloidal nanocrystals have been studied for decades because they can absorb and emit light very efficiently. They are also naturally compatible with printing techniques. However, turning them into high-performance electronic devices has been difficult, especially at very small scales.
The researchers solved this by combining electrohydrodynamic printing, a technique that uses electric fields to guide ink with extreme precision, with a clever chemical treatment applied immediately after printing.
This process allows the nanocrystals to bond together electrically without heating, which is crucial for protecting delicate materials and underlying electronics.
Using this method, the team printed silver nanocrystal lines just 70 nanometers wide—far thinner than a human hair—and produced conductive layers that perform almost as well as solid silver. Most impressively, they created fully printed infrared photodiodes smaller than 10 micrometers across, the smallest of their kind ever reported.
According to Professor Zhao, this work finally unlocks the real potential of nanocrystals. While scientists have long known they make excellent printable inks, the lack of precise, low-temperature fabrication methods held them back. This new platform makes it possible to build complex optoelectronic devices layer by layer, directly from solution.
The lead author, Zhixuan Zhao, explained that the key innovation is replacing traditional high-temperature sintering with a gentle chemical process that happens right after printing. This allows materials to remain intact while still achieving high electrical performance.
The research also involved collaboration with Professor Ji Tae Kim from the Korea Advanced Institute of Science and Technology, who highlighted the technology’s appeal for the semiconductor industry. Lower processing temperatures could make it easier to integrate new components with existing chips.
Looking ahead, the team plans to use this printing platform to develop optical metasurfaces, biosensors, and hybrid electronic systems.
By showing that complex infrared devices can be printed at the nanoscale, this research points toward a future where advanced sensors are not etched in expensive cleanrooms—but printed with remarkable precision.
