3DExpress: The World’s Smallest, Fully 3D-Printed, Infrared Photodetectors from HKU

This week’s 3DExpress starts with a breakthrough in Hong Kong, where a team of engineers created the smallest 3D printed sub-micron optoelectronics to date. This could mean that integrating multi-functional micro-nano devices will become a lot easier. Then, we get into a Kickstarter launch for an LPBF printer that is €8,500, continuing a trend of turning towards more affordable metal 3D printers. (See Mastrex, which announced its release of an LPBF printer for $39,000 at CES 2026.) Next, we cover Bambu Lab’s new copyright protocol, and finally, ADDMAN’s acquisition of Forecast 3D.

Printing the World’s Smallest Infrared Photodetectors

Researchers at the University of Hong Kong, led by Professor Leo Tianshuo Zhao from the Department of Electrical and Electronic Engineering, developed a room-temperature nano-printing platform capable of fabricating the smallest, fully-printed infrared photodetectors to date. Infrared photodetectors are sensors that detect heat and convert it into a measurable electrical signal, which can be used for seeing beyond visible light. Near-infrared technology is critical for applications like autonomous systems, biomedical sensing, and high-speed optical communications. However, conventional silicon-based CMOS technology cannot directly detect NIR wavelengths. The nano-printing platform created by the HKU team assembles solution-phase colloidal nanocrystals (NCs) and modifies their properties in situ, enabling the construction of advanced optoelectronic devices.

The versatile nano-printing platform that assembles solution-phase colloidal nanocrystals (NCs) and modifies their properties in situ (Image Credit: Tianshuo Zhao et al.)

Using electrohydrodynamic printing (EHDP) combined with surface chemical treatment, the team achieved unprecedented precision, printing silver nanocrystal lines as narrow as 70 nanometers and creating dense films with conductivity comparable to bulk silver, all without high-temperature processing. Most notably, the researchers demonstrated sub-10-micrometre all-printed IR photodiodes for the first time. The research represents a major step forward in high-resolution, multi-layer printing for electronic device integration.