US researcher develops temperature-responsive colour-changing material

Most colours in commercial and industrial products come from pigments which absorb, reflect light and fade over time. However, structural colours, which are found in animals like octopuses, use nanoscale structures to control how light reflects. Inspired by this efficient approach, Chanda has been researching how to create more vibrant, angle-independent colours without relying on chemical pigments for years.

His latest development addresses the challenges with dynamically tunable colour, complex designs and manufacturing challenges of structural colours, which may make it easier to commercially manufacture these materials. The concept holds immense promise for applications in thermal sensing, advanced textile engineering, camouflage and reconfigurable displays.

Chanda’s approach uses phase modulation of a multilayer stack composed of a phase-changing material and a high-index material on a reflective surface. When the temperature shifts, the way light moves through the material changes, causing the surface colour to change as well.

The technology combines several novel features including large area fabrication without complex lithography, which is an expensive patterning method, reversible colour change, precise control over dynamically customisable colour and broad dynamic range that spans a large portion of visible colour space

Earlier methods of developing structural colour often relied on expensive electrochromic materials, mechanical actuation or photonic crystals, all of which are hindered by limited tunability, complex fabrication steps, lithographic patterning requirements and angular sensitivity. Achieving dynamic colour switching in the visible range remains a significant challenge.

“The reliance on angle-dependent resonances or patterned nanostructures limits practical integration and scalability,” Chanda said. “Overcoming these barriers is critical for advancing tunable structural colour platforms toward real-world applications in flexible electronics, displays and wearable systems.”

This new method can be used for creating large textiles, complex surfaces, and temperature-sensitive consumer product labelling.

The design draws inspiration from animals like octopuses, which change colour by rearranging tiny structures in their skin rather than producing new pigments.

Chanda’s team created a layered design that can change colour without being affected by viewing angle or direction of the incident light. It uses a very thin layer of VO2, a material that changes phase from semiconductor to metal with temperature, placed on top of a thick aluminium layer to form a resonating cavity to trap and reflect light in a controlled way.

Pigment colourants control light absorption through a material’s electronic properties, which means each colour needs a new molecule and isn’t affected by the surrounding environment. Structural colourants, like those found in octopuses, work differently: they control the way light is reflected, scattered or absorbed based on the geometrical arrangement of nanostructures, making them sensitive to changes in their surroundings.

“Harnessing the reversible phase transition, the platform offers precise control over dynamically tunable colour, opening avenues for applications in temperature sensing, displays, tunable coloured fabrics and many other consumer products,” Chanda explained.

The bi-layer structure is made using magnetron sputtering to deposit the phase-change material, a process that uses plasma to deposit thin film. It also uses electron-beam deposition to deposit the metal layer, which melts material with a focused electron beam to create precise coatings. This combination allows the structure to be applied to flexible substrates, making it suitable for large-scale production and wearable applications.

Fibre2Fashion News Desk (RR)