Using Color-Changing, Photonic Crystals for Smart Sensing Application Development

June 02, 2020 by Luke James

Peacock features and butterfly wings have inspired a new generation of sensors.

It is a technology that is ingrained into the very fabric of the wings found on a butterfly and the feathers found on a peacock. Now, scientists at the University of Surrey are hoping that a new approach to creating color-changing crystals could help us predict earthquakes, among other things. 

A team of researchers led by scientists from the two British universities—the University of Surrey and the University of Sussex—has developed photonic crystals that can change color when exposed to changes in temperature, light, and other external factors. “Whereas nature has developed these materials over millions of years we are slowly catching up in a much shorter period”, Alan Dalton, Professor of Experimental Physics at the University of Surrey, said. 


Color-changing Photonic Crystals

With changes that can be seen unaided by the human eye, the green crystal can change color to blue when it is stretched or turn transparent when it is heated. Dalton said that the team’s research was inspired by nature and the way color is created in the bodies of some insects and birds. Although some colors in nature are created by pigmentation, others are produced by the way light hits the structure of a butterfly’s wings, for example. 


A peacock showing its feathers.
A peacock showing its feathers. Which the research team took inspiration from when developing the photonic crystals. 


"Our research here has taken inspiration from the amazing biomimicry abilities in butterfly wings, peacock feathers and beetle shells where the color comes from structure and not from pigments”, Professor Dalton said.

The team’s research set out to mimic this by creating a robust and low-cost sensor made from graphene that is able to respond sensitively to light, temperature, and other physical and chemical stimuli. 

Dr. Izabela Jurewicz, Lecturer in Soft Matter Physics at the University of Surrey's Faculty of Engineering and Physical Sciences, said, "This work provides the first experimental demonstration of mechanically robust yet soft, free-standing and flexible, polymer-based opals containing solution-exfoliated pristine graphene.”


Many Potential Applications

By tweaking the structure of these crystals, the research team hopes that they will be able to use the color-changing crystal as a sensor and integrate it into a variety of useful applications. 

These include the creation of intelligent packaging for food and drink, anti-counterfeiting measures, biometric applications like fingerprint analysis, bio-sensing, and healthcare safety, such as a wristband that changes color to indicate whether a healthcare practitioner has washed his or her hands before entering an examination room. 

 “While these crystals are beautiful to look at, we're also very excited about the huge impact they could make to people's lives”, Jurewicz added.