The core technology of the 3D printing process for smart contact lenses that can realize Augmented Reality (AR)-based navigation is Dr. Seol Seung-Kwon and Prof. .Lim Doo Chong. Ulsan National Institute of Science and Technology (UNIST) team.

A smart contact lens is a product that is attached to the human eye like a normal lens and provides various information. Lens-related research is mainly carried out for the diagnosis and treatment of health. Recently, Google and others have been developing smart contact lenses for displays that can implement AR. However, there are many obstacles to commercialization due to serious technical difficulties.

Electrochromic contact lenses are suitable for the application of augmented reality using smart contact lenses. ^[1] The low-power screens and the “Pure Berlin Blue” color are eye-catching with high price competition and fast contrast and color switching because the lens material. However, in the past, color was applied to the substrate as a film using the electroplating method. ^[2] limited the production of advanced screens that could display different information (letters, numbers, pictures)”.

KERI-UNIST’s breakthrough is a technology that can realize AR by printing micro patterns onto the lens screen using a 3D printer without applying voltage. The key is the meniscus of the ink used. The meniscus is a phenomenon in which a curved surface, free of water droplets, is formed on the outer wall, which breaks down due to capillary action by gentle pushing or pulling of water droplets with a certain pressure.

Berlin azure crystallizes through evaporation of the solvent in the meniscus formed between the microtip and the substrate. When the ink-filled micro nozzle and the substrate come into contact, a meniscus of ferric acid ferricyanide ink forms on the substrate. Heterogeneous crystallization of FeFe(CN)6 occurs on the substrate in the meniscus due to the spontaneous reaction of the precursor ions (Fe3+ and Fe(CN)3-) at room temperature. At the same time, the solvent evaporates on the meniscus surface.

As water evaporates from the meniscus, water molecules and precursor ions move to the surface of the meniscus by convective flow, forming a preferential accumulation of precursor ions on the outside of the meniscus. This phenomenon causes edge-enhanced crystallization of FeFe(CN)6; In order to obtain uniform printed PB patterns on the substrate, it is very important to control the factors affecting the crystallization of FeFe(CN)6 in the printing step. As with conventional galvanic plating, the substrate had to be conductive when voltage was applied, but the major advantage of using the meniscus phenomenon is that there is no limit to the substrate that can be used, as crystallization occurs by natural evaporation of the solvent.