Nanostructures demonstrating minimum feature sizes. (A) 3D model of a nonconnected “NANO” structure comprised of arrays of parallel nanowires; (B) SEM cross-sectional images of the “NANO” structure cut by a focused ion beam (FIB); (C) zoomed-in view of the letter “A” in (B); and (D) zoomed-in view of (C); (E) Four cross-sectional patterns of the “NANO” structure (in the x-z plane of (A)); (F) SEM images showing the trenches of the gel sample opened by an FIB-cut, where the positions of each letter are labelled. All cross-sectional images were taken at a substrate tilt angle of 52°.

Making many tiny things

18 March 2023

Fabricating high-resolution and complex objects with additive manufacturing across a wide range of materials is challenging. CUHK researchers synthesised very finely detailed objects from a wide range of materials using femtosecond light sheets and nanoparticle-laden hydrogels. 

The strategy works for ceramics, polymers, metals, semiconductors, and other materials while still maintaining fine feature sizes. This technique could enable nanofabrication across different classes of materials.

Professor Shih-Chi Chen of the Chinese University of Hong Kong led the team which conducted the research. Professor Zhao Yongxin from Carnegie Mellon University and Professor Zhao Ni from the CUHK Department of Electronic Engineering contributed.

the team developed a general strategy for fabricating 3D nanostructures with a library of materials including metals, metal alloys, 2D materials, oxides, diamond, upconversion materials, semiconductors, polymers, biomaterials, molecular crystals and inks. In their research, hydrogels patterned by femtosecond light sheets were used as templates that allow for direct assembly of materials to form designed nanostructures. By fine-tuning the exposure strategy, the features of the patterned gel and the kinetic effects, the team made 2D and 3D structures of 20- to 200-nm resolution.

To demonstrate the capabilities of the new method, the team fabricated nanodevices including encrypted optical storage, diffractive optical elements and microelectrodes, to showcase the precision and the designed functions. The optical storage device set a new record for storage density (1.14 petabit/cm3, approximately three orders of magnitude higher than the previous record), and simultaneously set a new record for data-writing speed (84 Mbit/s), owing to the high-speed nature of the femtosecond projection method. The method points towards a systematic solution for nanofabrication across different classes of materials and opens up further possibilities for the design of nanodevices. The findings were published in Science.