BENGALURU: Researchers at the Indian Institute of Science (IISc) developed flexible films that reveal bright colours without any use of pigments–like mollusc shells and peacock feathers that possess inherently vibrant colours. When stretched, the film can change colours as a response to mechanical deformation. These films can be used for various applications.
To design these films, scientists devised a novel, cost-effective, scalable single-step technique involving evaporating gallium metal (liquid) to form nano-sized particles on a flexible substrate, which has not been experimented with before given its high surface tension barrier. The method allows the simultaneous production of multiple structural colours responsive to mechanical stimuli.
The tension barrier that restricts the formation of gallium nanoparticles is overcome by using the properties of a substrate called polydimethylsiloxane (PDMS)--a biocompatible polymer.
PDMS is made by mixing two liquid-like components – an oligomer and a cross-linker – which react with each other to form a solid polymer. The scientists found that the unreacted portion of the oligomer, which is still in a liquid state, played a crucial role in stabilising the formation of gallium nanoparticles on the substrate. “When this substrate is then stretched, the liquid-like oligomers seep into the gaps between the nanoparticles, changing the gap size and their interaction with light, resulting in the observed change in colouration,” the release said.