3D printing smart contact lens AR displays
Researchers in Korea have developed a technique to 3D print the display on a smart contact lens.
The Smart 3D Printing Research Team at KERI in Changwon, led by Dr. Seol Seung-Kwon, and Professor Lim-Doo Jeong’s team at Ulsan National Institute of Science and Technology (UNIST) developed the smart contact lenses for augmented reality (AR)-based navigation
The key to the KERI-UNIST work lies in printing micro-patterns onto a smart contact lens using a 3D printer without applying voltage. The key is the meniscus of the ink.
Prussian blue ink is crystallized through solvent evaporation in the meniscus formed between the micronozzle and the substrate. The meniscus of the acidic-ferric-ferricyanide ink is formed on the substrate when the ink-filled micronozzle and substrate come in contact.
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Heterogeneous crystallization of the ink (FeFe(CN)6) occurs on the substrate within the meniscus via spontaneous reactions of the precursor ions (Fe3+ and Fe(CN)3−) at room temperature. Simultaneously, the solvent evaporation is occurred at the meniscus surface.
When water evaporates from the meniscus, the water molecules and precursor ions move toward the meniscus surface by convective flow, accumulating the precursor ions in the outer part of the meniscus.
This phenomenon induces the edge-enhanced crystallization of ink; this is crucial for controlling the factors that influence the crystallization of FeFe(CN)6 in the printing step to obtain uniformly printed patterns on the substrate.
With conventional electroplating techniques, the substrate has to be a conductor when voltage was applied, which is a problem with contact lenses. Using the meniscus phenomenon means here is no restriction on the substrate that can be used because crystallization occurs by natural evaporation of the solvent.
Through the precise movement of the nozzle, the crystallization of Prussian blue forms the micro-patterns for the display. Patterns can be formed not only on flat surfaces but also on curved surfaces and the micro-pattern technology has a resolution of 7.2 microns.
“Our achievement is a development of 3D printing technology that can print functional micro-patterns on non-planner substrate that can commercialize advanced smart contact lenses to implement AR,” said Dr. Seol Seung-Kwon’s of KERI. “It will greatly contribute to the miniaturization and versatility of AR devices.”
The main expected application area is navigation for AR, but the technique could also be used by companies working on batteries and biosensors that require micro-patterning of Prussian blue.
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