The core technology for smart contact lenses that can perform AR-based navigation using a 3D printing process has been introduced by a joint research team affiliated with UNIST. The research team claims that the new smart contact lenses can be worn in a person’s eye just like regular contact lenses.

The expensive cost, experimental technology and cumbersome design of today’s AR gadgets are some of the drawbacks that make it challenging for them to enter the market. By contrast, because they can be worn in a person’s eye, smart contact lenses are both economical and practical. World leaders such as Google are now developing smart contact lenses that can use augmented reality. Due to significant technical difficulties, obstacles still stand in the way of the effective and efficient commercialization of research.

Energy-efficient electrochromic (EC) displays that can be powered with little power are excellent for using augmented reality with smart contact lenses. Because of its uniform coloring, fast kinetics, high optical contrast, numerous color states (blue, white and green), environmental friendliness and affordability, Prussian blue (PB) is recognized as one of the most attractive EC materials.

However, the research team pointed out that due to the difficulties of micropatterning PB on the contact lens, this technology needs to be improved to display words or images required for display on smart AR contact lenses.

The joint research team explored ways to produce micro-patterns from PB without using an electroplating process, and as a result they developed a simple and efficient printing strategy. They used meniscus-guided printing with an acidic iron-iron-ferricyanide ink made from FeCl3, K3Fe(CN)6 and HCl. The meniscus of the acidic iron-iron-ferricyanide ink is crucial in this situation.

As with conventional electroplating, the substrate must be a conductor when it is live. However, with the meniscus phenomenon, no limitation of the substrate can be used because crystallization occurs through the natural evaporation of the solvent.

Scientists noted, “Our micro-pattern technology is very fine (7.2 microns) and can be applied to AR smart contact lens displays, and the color is continuous and uniform.”

“The role of smart contact lenses is most anticipated in areas such as navigation. Through experiments, researchers successfully demonstrated PB-based EC displays in a smart contact lens with navigation function. The device could show directions to the destination to the user on the EC display by receiving GPS coordinates in real time.”

Electrochromic (EC) display for navigation system embedded in a contact lens
Electrochromic (EC) display for navigation system embedded in a contact lens.

“While thin glass ITO was used for the EC display in this study, it can be further developed to clatter transparent electrodes, such as graphene, onto flexible and printed EC materials. We believe our new strategy will serve as a attractive method for realizing PB-based EC displays and various functional devices with micro-PB patterns.”

Magazine reference:

  1. Je Hyeong Kim, Seobin Park, Jinhyuck Ahn, et al., “Meniscus-Guided Micro-Printing of Prussian Blue for Smart Electrochromic Display,” Advanced Science (2023). DOI: 10.1002/advs.202370017