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Micro pattern introduces colour reflective display

Posted: 20 May 2014 ?? ?Print Version ?Bookmark and Share

Keywords:KAIST? opal? pattern? reflective display?

The Korea Advanced Institute of Science and Technology (KAIST) has taken a step closer in the commercialisation of photonic crystals with a practical patterning technology.

Led by the late professor Seung-Man Yang, the team developed a micro-pattern technology using photolithographic process. This could be used as a core material for the next-generation reflective display that is clearly visible even under sunlight. Since it does not require a separate light source, a single charge is enough to last for several days.

Until now, many scientists have endeavoured to make photonic crystals artificially. However, most were produced in a lump and therefore lacked efficiency. One roadblock to commercialisation is the low mechanical stability of the formed structure.

In order to solve these problems, the research team copied the nano-structure of opals. The mineral opal does not possess any pigments, but it appears colourful to our eyes. This is because only a particular wavelength is reflected due to the regular nano-structure of its surface. The material that causes selective reflection of the light is called photonic crystals.

Glass beads were arranged in the same nano-structure as the opal on top of the photoresist material undergoing photocuring by ultraviolet light. The glass beads were installed in the photoresist materials, and UV light was selectively exposed on micro regions. The remaining region was developed by photolithographic process to successfully produce photonic crystals in micro-patterns.

Nano glass bead arrangement

Figure 1: Opal [left] and the nano glass bead arrangement structure within the opal [right]. Source: KAIST

"Combining the semiconductor process technology with photonic crystal pattern technology can secure the practical applications for photonic crystals," said research co-author and KAIST Chemical and Biomolecular Engineering Department's Professor Sin-Hyeon Kim.

"This technology can be used as the key optical material that configures the next generation reflective colour display device with very low power consumption," Kim added.

Photonic crystal micro pattern

Figure 2: Photonic crystal micro-pattern that reflects two different crystals (Red, Green) [left] and pixelated pattern of photonic crystal in three primary colours (Red, Green, Blue) [right] that is applicable to reflective displays. Source: KAIST

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