A team of scientists from KERI (Korea Electrotechnology Research Institute) and the Ulsan National Institute of Science and Technology (UNIST) has been able to 3D-print smart contact lenses without applying voltage. 

“Our achievement is a development of 3D-printing technology that can print functional micro-patterns on non-planar substrate that can commercialise advanced smart contact lenses to implement AR,” said Dr Seol Seung-Kwon’s of KERI. 

“It will greatly contribute to the miniaturisation and versatility of AR devices.”

Smart contact lenses is a technology that could allow people to directly visualise digital environments, without the need for AR glasses, which are expensive and have been known to cause side-effects such as nausea. 

The main expected application area is navigation. Simply by wearing a lens, navigation unfolds in front of a person’s eyes through AR. Games such as the popular ‘Pokemon Go’ can also be enjoyed with smart contact lenses, not smartphones.

However, creating smart contacts comes with its own set of challenges. 

In order to implement AR with smart contact lenses, the displays need to be able to work with low power. For this reason many researchers gravitate towards a “Pure Prussian Blue” colour, which is affordable and has a high contrast.

Nonetheless, in the past, the colour was coated on the substrate using the electroplating method, which limited the production of advanced displays that can express various information, such as letters, numbers or images. 

The achievement of the KERI-UNIST teams lies in the fact that it is a technology that can realise AR by printing micro-patterns on a lens display using a 3D printer without applying voltage. 

The key to the breakthrough lies in the meniscus of the ink used.

The meniscus is a phenomenon in which a curved surface is formed on the outer wall without water droplets bursting due to capillary action when water droplets are gently pressed or pulled with a certain pressure.

The meniscus is also the origin of the Prussian blue, which is obtain through solvent evaporation. 

Through the precise movement of the nozzle, the crystallisation of Prussian blue is continuously performed, thereby forming micro-patterns. Patterns can be formed not only on flat surfaces but also on curved surfaces, such as contact lenses. 

The research team’s micro-pattern technology is very fine (7.2 micrometres), which allows it to be applied to smart contact lens displays for AR, and maintain a colour that is continuous and uniform.

The research team believes that this achievement will attract a lot of attention from companies related to batteries and biosensors that require micro-patterning of Prussian blue as well as the AR field. 

The related research results were recently published in an article in Advanced Science.