Structural Coloration

Prelims: Science and technology | Current events of national and international importance

Why in news?

Recently, scientists at the Centre for Nano and Soft Matter Sciences (CeNS) have now found a way to harness a property known as structural coloration.

Centre for Nano and Soft Matter Sciences (CeNS), an autonomous institute of Department of Science and Technology (DST) under Ministry of Science and Technology is located in Bengaluru.

• Structural coloration – It refers to colors in materials that is caused a result of the physical structure of the material.
  • Example: The colour of the peacock’s feathers & radiant wings of a butterfly change depending on how you look at it, varying between shimmering blues and greens.
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• Research work – It explores how size-reduced monolayers of self-assembled polystyrene (PS) nanospheres exhibit angle-dependent optical properties due to collective light-matter interactions within the monolayer.

Structural colors arising from nanoscale geometry can be finely tuned by varying both the size of colloidal spheres and the angle of light incidence.

• Polystyrene Nano spheres - These are about 400 nanometers wide which naturally arrange themselves into a flat, hexagonal pattern when floated on water.
• This self-assembly, driven by simple surface forces, results in what the scientists call a close-packed monolayer.
• Reactive ion etching — It is a kind of nano-scale sandblasting, to gently shrink the spheres without disturbing their neat arrangement once a monolayerr is formed.

• This size reduction leads to a “non-close-packed” layout.
• Property of light – It behaves differently as it hits the altered surface.
• When light reflects off this nanostructured layer, its interaction with the tiny spheres causes certain wavelengths (colors) to be amplified or diminished.
  • For instance, by tilting the surface or changing the viewing angle, the reflected color shifts—typically towards blue.

• This phenomenon is predictable and tunable due to the way in which the spacing and size of the spheres affect light’s path.
• Advantages – They do not rely on harmful dyes or complex fabrication processes and are durable and vibrant.
• Applications – It is used to create tunable color-shifting materials using tiny plastic beads that can be used for
  • Wearable sensors, anti-counterfeit tags, display technologies and even eco-friendly paints.

Reference

PIB| Tuning Structural Coloration in Laboratory