Researchers at the Indian Institute of Science (IISc) have developed flexible films that mimic the vibrant colours found in mollusc shells and peacock feathers without the use of pigments. These films can change colour when subjected to mechanical stress, making them versatile for various applications.

The innovative technique involves depositing liquid gallium metal to create nano-sized particles on a flexible substrate, enabling the production of multiple structural colours simultaneously. Previously, the high surface tension of gallium hindered such applications.

To overcome this challenge, the researchers utilized polydimethylsiloxane (PDMS), a biocompatible polymer substrate. PDMS, formed by blending two liquid components that react to form a solid polymer, stabilizes the formation of gallium nanoparticles. The unreacted liquid-like oligomers play a crucial role in this stabilization process.

When the substrate is stretched, the liquid-like oligomers fill the gaps between nanoparticles, altering their size and light interaction, resulting in colour changes. This mechanism underlies the observed variations in colouration.

In summary, the researchers' novel approach exploits PDMS's properties to facilitate the formation of gallium nanoparticles that respond dynamically to mechanical stress, producing vivid structural colours in flexible films. This innovation presents a sustainable and efficient alternative to traditional pigment-based colouration methods, holding promise for a wide range of applications.