Inspired by the structure of insect eyes, Taiwanese scientists have developed new materials that could improve the color and effectiveness of the bright, reflective coatings used for safety purposes on road signs, bicycles and clothing.

Inspired by insects' compound eyes, researchers coated glass microspheres with smaller balls of silica, resulting in a brilliantly colored, retroreflective material. Image credit: Pixabay. Retroreflective materials, including some tapes and road paints, operate by bouncing light back toward the original source, such as a car’s headlights, making them bright and easy to see. Existing retroreflectors are usually made with glass microbeads and microprisms. While dyes, pigments and plastic layers are often added for color, they tend to reduce the reflection of light, and the colors can fade over time.

Hongta Yang and fellow engineers from National Chung Hsing University turned to the compound eyes of insects for a new way to address these limitations. The researchers evenly coated an array of glass microspheres with smaller balls of silica, resulting in a brilliantly colored, retroreflective material. The color can be adjusted by changing the size of the silica crystals, and brightness can be boosted by adding layers.

At 250 nanometers and 40 layers deep, the crystals appear bright green and reflect more light than commercial coatings with no color. In addition to boosting the brightness of objects for safety reasons, the researchers say that by reflecting rather than absorbing light, the material could be applied to buildings to reduce the urban heat-island effect.