Prof Li Pei

Impact Highlights

The development of indelible ink by PolyU researcher has had significant positive effects on the economy, industry and food safety. Enough of this ink is sold annually to print 30 billion food and drink packages. A new company Xianhong, launched in 2013 to develop and commercialize the ink, is providing tamper-proof expiry dates and product information for some of China’s largest food and beverage manufacturers. Our patented award-winning ink has enabled Xianhong to rapidly grow with over 60 employees now working on ink-related business. Xianhong listed on the stock market in 2016. Annual sales revenue was RMB 150M in 2018 generating a net profit of RMB 20.5M. Three of the top dairy companies in the world (Nestle, Yili, Mengniu) use the ink, and sales cover 14% of the Chinese fast-moving goods industry. Modified ink is used by 23% of China’s cable and wire industry for its high rub-resistance.

Professor Pei Li’s fundamental research at PolyU into the design and synthesis of nano- and micro-particles, and particularly her work on nano-coatings, led to the development of a new tamperproof ink formulation. Professor Li’s research group developed several new methods of creating core-shell and hybrid polymer particles (for example, hydrophobic cores with hydrophilic shells). This platform technology has a wide range of applications including the creation of antibacterial coatings on various substrates.

This research attracted Hallyuen Holdings’ attention as they were trying to find a solution for long-standing industry challenge – how to protect product labels. The company believed that Li’s research on materials and interfacial properties could be exploited to develop an ink that would, in contrast to traditional formulations, permanently bind with a plastic substrate. In 2011, the company funded Professor Li and her team to create a tamperproof ink and printing method that could be applied on plastic substrates such as food packaging.

After over two years of research and development, Professor Li devised a breakthrough nano-based ink formulation in 2013. The novel feature of the new ‘anti-erasing’ ink’s composition was to include two or more colorants, at least one being hydrophobic. They are able to phase-separate during the printing process. This ink composition yields a double-layered, double-colored print when printed on multilayered plastic packaging. The first layer is the surface colorant, which can be removed by an organic solvent. However, the hydrophobic colorant stains non-porous substrates such as low-density polyethylene (LDPE) and therefore remains, leaving a watermark of the surface print which is highly resistant to chemical and physical stress.

Professor Li and her team’s subsequent research has expanded on this initial solution to develop a series of ink formulations including indelible inks, migration-resistant inks, oil-resistant inks, alcohol-resistant inks, rub-resistant inks and water-resistant inks and hence a plethora of possible applications.