To design these films, the team devised a novel cost-effective and scalable single-step technique that involves evaporating gallium metal to form nano-sized particles on a flexible substrate. Their method allows the simultaneous fabrication of multiple structural colors responsive to mechanical stimuli.

The team has also shown how these films can be used for a variety of applications, from smart bandages and movement sensors to reflective displays.

"This is the first time that a liquid metal like gallium has been used for photonics," says Tapajyoti Das Gupta, Assistant Professor in the Department of Instrumentation and Applied Physics (IAP), and corresponding author of the study published in Nature Nanotechnology.

Some natural objects like gemstones, mollusk shells or peacock feathers are inherently colorful. Their colors emerge from the interaction of light with micro- or nano-structures arranged periodically, such as tiny silica spheres in opal, calcium carbonate-based platelets in mollusk shells, and segmented ribbons atop cylindrical structures in peacock feathers.

Nature-inspired structurally colored materials have found broad applications in displays, wearable electronics, visual sensors, and anti-counterfeiting tags. In recent years, scientists have been trying to design materials that can change color in response to an external mechanical stimulus.