A team of researchers in Bengaluru has discovered a way to create tunable colour-shifting surfaces inspired by nature’s vibrant displays—like the feathers of a peacock or the wings of a butterfly.
At the core of this breakthrough is a phenomenon known as structural coloration, where colours are produced not by pigments but by the physical structure of a surface that interacts with light.
The study, carried out at the Centre for Nano and Soft Matter Sciences (CeNS), an autonomous institute under the Department of Science and Technology (DST), demonstrates how light can be manipulated at the nanoscale to produce colours that do not fade over time.
Inspired by Nature
Unlike dyes or paints, structural colours arise when light waves are reflected, refracted or scattered by microscopic patterns. This is what gives the peacock its iridescent blues and greens that change with the angle of light.
The scientists at CeNS have used polystyrene nanospheres, each about 400 nanometres wide, to replicate this effect. These tiny beads, far smaller than a grain of sand, naturally arrange themselves into a hexagonal pattern when placed on water, forming what is called a close-packed monolayer.
Fine-Tuning Colours with Light and Geometry
Once this layer is formed, the team uses a technique called reactive ion etching—similar to a nano-scale sandblasting process—to slightly reduce the size of the spheres while maintaining their orderly arrangement. This changes how light interacts with the surface.
As light strikes this nanostructured layer, certain wavelengths are enhanced or suppressed. This means the reflected colour can be adjusted—simply by tilting the surface or changing the viewing angle, shifting it towards shades like blue.
The result is a vibrant, durable colour that does not fade under sunlight or over time, unlike traditional chemical dyes.
Scalable and Sustainable
What makes this research notable is its practicality. The technique relies on self-assembly, a low-cost process where the particles naturally arrange themselves—making it scalable for large-area production without complex machinery.
According to the researchers, this approach could find applications in wearable sensors, anti-counterfeit labels, flexible displays, and even eco-friendly paints that do not release harmful chemicals into the environment.
The findings, recently published in the Journal of Applied Physics, highlight how understanding light’s interaction with matter at the nanoscale could lead to new materials with customisable optical properties.
Bridging Science and Application
By showing how tiny changes in the geometry of these nanospheres influence how light is reflected, the CeNS team has opened new possibilities for advanced optical materials.
Such materials could eventually replace conventional pigments in various industries, helping reduce environmental impact while providing vibrant, long-lasting colours.
