New microscale 3D printer for multi-level anticounterfeiting labels

The team led by Dr Ji Tae Kim from the Department of Mechanical Engineering at the University of Hong Kong (HKU) has developed a high-precision 3D printing method that can produce new polarisation-encoded 3D anticounterfeiting labels. This new 3D label can encrypt more digital information than a traditional 2D label. The work has been published in Nano Letters in an article entitled "Three-Dimensional Printing of Dipeptides with Spatioselective Programming of Crystallinity for Multilevel Anticounterfeiting."

Diphenylalanine (FF), a species of dipeptides, was chosen as a material for data encryption due to its unique optical properties. Dr Jihyuk Yang from the Department of Mechanical Engineering, HKU, explained: "FF has long attracted great attention to neuroscientists due to its association with Alzheimer's disease. Recently, FF is emerging as a new electronic and photonic device material due to its unique properties -- e.g. piezoelectricity and optical birefringence -- arising from crystalline nature." Dr Yang is the first author of the paper.

"Our new 3D printing method combined with nature-driven molecular self-assembly can print multi-segmented 3D FF micro-pixels with programmed crystallinity for high-density data encryption. By utilising different responses of the amorphous and crystalline segments to polarised light, a tiny single 3D pixel can encrypt a multi-digit binary code consisting of "0" and "1." The information capacity can be increased to 2¹¹ with a single eleventh-segmented freestanding pixel on a tiny 4 µm² area which is 1000 times smaller than a hair strand," said Dr Ji Tae Kim. He believes that 3D printing technology can be effectively used to customise security labels on-demand anywhere and anytime, contributing to strengthening the information security of individuals and companies.