In this research, we were able to finely distribute graphene at distances comparable to the wavelengths of visible light and showed how adding tiny amounts of the two-dimensional wonder-material leads to emerging new capabilities."Joseph Keddie, University of Surrey

Scientists have taken inspiration from the biomimicry of butterfly wings and peacock feathers to develop an innovative opal-like material that could be the cornerstone of next generation smart sensors.

An international team, led by scientists at the universities of Surrey and Sussex in the UK, has developed color-changing, flexible photonic crystals that could be used to develop sensors that warn when an earthquake might strike next. The wearable, robust and low-cost sensors can respond sensitively to light, temperature, strain or other physical and chemical stimuli, making them an extremely promising option for cost-effective smart visual sensing applications in a range of sectors, including healthcare and food safety.

In a paper published in Advanced Functional Materials, the scientists outline a method for producing photonic crystals containing a minuscule amount of graphene, resulting in a wide range of desirable qualities with outputs directly observable by the naked eye. Intensely green under natural light, the extremely versatile sensors change color to blue when stretched or turn transparent after being heated.

"This work provides the first experimental demonstration of mechanically robust yet soft, free-standing and flexible polymer-based opals containing solution-exfoliated pristine graphene. While these crystals are beautiful to look at, we're also very excited about the huge impact they could make to people's lives," said Izabela Jurewicz, lecturer in soft matter physics at the University of Surrey's Faculty of Engineering and Physical Sciences.

"Polymer particles are used to manufacture everyday objects such as inks and paints. In this research, we were able to finely distribute graphene at distances comparable to the wavelengths of visible light and showed how adding tiny amounts of the two-dimensional wonder-material leads to emerging new capabilities," said Joseph Keddie, professor of soft matter physics at the University of Surrey.

"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. Whereas nature has developed these materials over millions of years, we are slowly catching up in a much shorter period," said Alan Dalton, professor of experimental physics at the University of Sussex's School of Mathematical and Physical Sciences.

These novel photonic crystals could have many potential applications. For example, they could be used as time-temperature indicators (TTI) for intelligent packaging, giving a visual indication if perishables, such as food or pharmaceuticals, have experienced undesirable time-temperature histories. The crystals are extremely sensitive to even a small rise in temperature between 20°C and 100°C.

They could be used for fingerprint analysis, as their pressure-responsive shape-memory characteristics are attractive for biometric and anti-counterfeiting applications. Pressing the crystals with a bare finger can reveal fingerprints with high precision, showing well-defined ridges from the skin.

They could be used as tissue scaffolds for understanding human biology and disease. If functionalized with biomolecules, they could act as highly sensitive point-of-care testing devices for respiratory viruses, offering inexpensive, reliable, user-friendly biosensing systems. Their mechanochromic response could also allow them to be used as body sensors for improving technique in sports players. They could even be used to produce a wrist band that changes color to indicate to patients if their healthcare practitioner has washed their hands before entering an examination room.

The universities of Surrey and Sussex are now working with the Sussex-based company Advanced Materials Development (AMD) Ltd to commercialize this technology.

"Given the versatility of these crystals, this method represents a simple, inexpensive and scalable approach to produce multi-functional graphene infused synthetic opals and opens up exciting applications for novel nanomaterial-based photonics. We are very excited to be able to bring it to market in near future," said John Lee, CEO of Advanced Materials Development (AMD) Ltd.

This story is adapted from material from the University of Surrey, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier. Link to original source.