Research Highlight

Subject Category: Device applications

NPG Asia Materials research highlight; doi:10.1038/asiamat.2009.14
Published online 19 October 2009

Photonic crystals: Desktop manufacturing

The production of large-area photonic crystals using a standard ink-jet printer offers a cost-efficient solution for optical coatings and photonic devices.

Photonic crystals have potential for use in applications that exploit the reflection of light at specific wavelengths. However, the production of large-scale, three-dimensional photonic crystal arrays can only be achieved at present using complex and expensive equipment. Researchers from the Institute of Chemistry at the Chinese Academy of Sciences1 have now developed a method for fabricating large-scale arrays of photonic crystal using a conventional ink-jet printer.

The preparation of a precise crystalline structure is critical for high-performance photonic crystal. Self-assembly methods using uniform spheres are particularly useful for this purpose, since the natural periodic stacking order of the spheres results in photonic crystal with well-defined reflection bands.

The researchers, led by Yanlin Song, developed a fast and efficient method to print photonic crystal films by this self-assembly technique using a common ink-jet printer. The method allows photonic crystal to be printed over a large area on a variety of surfaces. “Our method is flexible and can be used on paper, aluminum, plastic, silicon and glass substrates,” says Song.

The latex spheres used in their process were 180 to 280 nm in diameter, and the precise diameter of the spheres determined the color of the printed structures. To facilitate an ordered arrangement of the spheres, as well as increase the stability of the photonic crystal thus formed, the spheres were first covered with a hydrophilic polyacrylic shell that softened in solution, allowing the spheres to interact and bind with neighboring spheres. This interaction supports the self-guided assembly of the photonic crystal, eliminating the need for any external stimulus once the ink solution has left the printer nozzle. The use of inks made from spheres of different sizes caused the reflection bands of the photonic crystals to shift through the color spectrum, allowing multicolor images to be produced (Fig. 1).

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Fig. 1: An ink-jet-printed photonic crystal film made from latex spheres with diameters of 220 nm (green) and 280 nm (red). The film consists of a number of layers, reaching a printed thickness of about 7 μm.
Reproduced with permission of the Royal Society of Chemistry.

The ease of fabricating these nanoscale structures, using common ink-jet printers, has opened a range of potential applications, not only in photonic devices but also in optical sensors and other coatings.

The researchers aim to optimize their printing method for more complex structures. “To achieve more complex and high-resolution patterns, better control of the droplet position on the substrate is important,” says Song.

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References

  1. Cui, L., Li, Y., Wang, J., Tian, E., Zhang, X., Zhang, Y., Song, Y., & Jiang, L. Fabrication of large-area patterned photonic crystals by ink-jet printing. J. Mater. Che. 19, 5499 (2009).

This research highlight has been approved by the author of the original article and all empirical data contained within has been provided by said author.

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