A precise flash of inspiration
Chen Shih-chi’s nanoprinter rewrites the rules of nanoscale 3D manufacturing
11 September 2026
This is the first part of a series in which CUHK in Focus talks to leaders of the pioneering CUHK projects selected for the 2026 round of the Hong Kong government’s Research, Academic and Industry Sectors One-plus (RAISe+) scheme. With up to HK$100 million in matching funds awarded to each approved project, RAISe+ accelerates the translation of university R&D into high-impact commercial outcomes. To date, 16 CUHK projects have secured funding under the scheme.
With 3D printing technology making leaps and bounds, one can print anything nowadays, from figurines to intricate machines. The exactitude of such printers represents a major advance in precision manufacturing, enabling professionals in the medical field and beyond, to fabricate custom parts from medical devices to components for direct patient care. However, nanoscale precision has long remained trapped by speed and cost bottlenecks.
“This technology is useful, highly impactful – but simply too expensive for widespread adoption,” says Professor Chen Shih-chi of CUHK’s Department of Mechanical and Automation Engineering. To overcome these barriers, Professor Chen and his team at the CUHK InnoCentre for Perceptual and Interactive Intelligence (CPII) have developed the Femtosecond Projection NanoPrinter to replace existing solutions regarding two-photon lithography. By combining light-sheet technology with advanced photopolymerisation, their platform can not only print at much higher speeds and significantly reduce manufacturing costs, but also support a diverse range of materials, opening up a new horizon for nanoscale 3D manufacturing.
Crafting with a light sheet: overcoming the nanoscale bottleneck
The process of conventional two-photon lithography is simple enough to explain: an optical scanner steers a laser to cure translucent photo resins point by point, which eventually form an object. This is an example of photopolymerisation, a printing process in which objects are created from a light-sensitive polymer.
The problem, however, lies in the size and complexity of objects to print, as well as high costs. Although current commercial printers using this technology can create complex three-dimensional objects, this process is slow and very expensive. For instance, producing a single component measuring just 5 mm in size – roughly the width of a single pea – can take up to a week and cost as much as HK$50,000.
“People can use the machine to demonstrate all kinds of amazing things at nanoscale for material, medical or biological applications, but they can’t make a widespread impact because it’s just too expensive,” says Professor Chen. With such production bottlenecks, uptake has been limited.
The professor’s brainwave in approaching this problem was simple, but very effective: instead of a single pinpoint laser beam, why not broaden that power into something more malleable? “We spread out the energy into a very, very thin light sheet,” he says. “On that light sheet, we make it programmable.” The light sheet varies its displayed patterns as it moves, fashioning the structure from bottom up. This process, known as “projection two-photon lithography”, allows for greater control and results in a dramatic leap in manufacturing throughput, speeding up production by up to a thousandfold.
Professor Chen also notes how the increase in printing speed helps massively cut down production costs. “The laser is very expensive, a million [HK] dollars or two apiece, but it also has a finite operational lifespan of around 30,000 hours.” By dramatically reducing laser time per minuscule component, the new platform reduces machine wear and tear, contributing to the slashing in production costs by up to 95%.
Beyond plastics: hydrogels, nanoparticles and electrical conductivity
Besides higher speed and lower costs, Professor Chen’s project has also expanded the printer to fit different materials. While conventional two-photon printers are often restricted to specific photopolymers, the new printer can use hydrogel as a medium to form complex 3D structures containing different materials. Widely used in medical scenarios, especially in gynaecological contexts, hydrogel has captured the attention of chemists and material scientists for its flexibility and restorative properties. For Professor Chen’s project, the team successfully fabricated a hydrogel structure as fine as 20 nm in size – roughly one-5000th of the thickness of a single sheet of paper. “We can construct very complex, enlarged three-dimensional structures with precision, making for a futuristic fabrication platform.”
Professor Chen stresses that this is just the beginning: the team has experimented by embedding nanoparticles of different materials, such as metal into the hydrogel to test whether the printer can work beyond bland white plastic. The initial results have been encouraging: “Not only are they assembled with high density and high resolution, but their functions are preserved,” says Professor Chen. “After shrinking, they remain conductive” – keeping the precious metal trait intact. The team plans to enhance the printer’s reliability and publish peer-reviewed papers based on further research.
From MIT to CUHK: translating deep tech to market
Professor Chen’s academic journey reflects CUHK’s status as a destination of choice for top global scientific talent. Having grown up in Taiwan and earned his master’s and doctoral degrees in mechanical engineering from the Massachusetts Institute of Technology (MIT), he completed postdoctoral research in optical solutions for medicine at the Wellman Center for Photomedicine at Harvard Medical School. A visit to Hong Kong introduced Professor Chen to CUHK’s world-class research ecosystem, cementing his resolve to make the university his next base.
“Hong Kong has some of the best resources in research,” he tells CUHK in Focus, adding that research in engineering is particularly well-supported here, on a par with his previous experiences in leading US institutions. “Plus, it’s supported by the rapid development of the Greater Bay Area, and the Chinese economy and technology.” Nowhere is this more evident than the RAISe+ scheme, which has provided Professor Chen’s spin-off venture, Astra Optics Limited, with HK$37 million in matching funds to continue commercialising the nanoprinting system and introducing the industry to the team’s work.
While the RAISe+ funding is a good start, the team sees substantial opportunity to advance the nanoprinter further: beyond looking into its biomedical and optical applications, they are leveraging Professor Chen’s new supervisory role at the Centre for Heterogeneous Integration and Production (CHIP), a new InnoHK Centre focused on semiconductors, to drive new synergistic applications such as photonic integrated circuits. The Centre, in collaboration with National University of Singapore, operates under SEAM@InnoHK, the third research cluster of the HKSAR government’s flagship innovation initiative. It aims to advance next-generation technologies in sustainable development, energy, advanced manufacturing and materials.
“Hopefully, in two or three years, the company’s valuation will increase, laying a stronger foundation for us to make more technological leaps,” says the professor, looking forward to the many possibilities.
By Chamois Chui
Photos by Steven Yan
