Replicating nature’s ability to reflect light promises new photonics materials

23 Feb 2017

Surrey team develops ceramics that mimic "butterfly wing" structures; with patents filed, and commercial partner identified.

Researchers from the University of Surrey, UK, have developed a technique to mimic one of nature’s greatest achievements – natural structural colour. Following research into explaining the physics behind photonic band gaps in structured photonic materials, the team has developed a new method to characterize the internal structures of natural materials and replicate their interaction with light using 3D printing of ceramics.

The internal structure of materials and their local-self uniformity dictates their ability to diffuse absorb, reflect and transmit light. This study has been published in Nature Communications

During this study, the researchers – Marian Forescu, Steven Sellers, Weining Man and Shervin Sahba – discovered a direct relationship between the uniformity of the material’s internal structure at wavelength scales and its ability to block certain wavelengths in natural materials. They then developed a new mathematical method to measure which photonic structures best control the propagation of light – enabling the design of new materials with different functionalities dependant on need.

The team then developed the first ever amorphous gyroid (triamond) structure with bandgaps, which is similar to the structuring found in some butterfly wings, by 3D ceramic printer. In a similar way to structures found in nature, these artificial structures can reflect and absorb light, sound and heat wave lengths leading the way for the creation of heat-rejecting window films and paints to improve the energy efficiency of buildings and vehicles.

Lead author Marian Florescu, from the University of Surrey, commented, “It is truly amazing that what we thought was an artificial design could naturally be present in nature. This discovery will impact how we design materials in the future to manipulate their interaction with light, heat and sound.”

About the research

The major research objectives included:

• A new unifying concept and classification scheme, called "local self- uniformity", which provides a fundamental foundation for classifying network structures. It classifies all networks from crystalline to chaotic across a single spectrum and, say the team, “represents a new frontier in design of the disordered materials across the physical sciences”.
• Discovery and exploration of new photonic structures able to support large photonic bandgap, in both two and three-dimensions. Employing local self-uniformity, the introduction of the new class of amorphous networks, amorphous single-gyroid (or triamond) structures. This novel structure is the trivalent relative of amorphous diamond and displays by construction a high-degree of local self-uniformity. The group demonstrated the presence of large photonic PBGs in this structure by fabricating the first-ever 3D-printed alumina photonic band gap material.
• A demonstration that a material's optical properties, particularly the existence of complete photonic band gaps, are closely connected with its structure via its local self-uniformity and that nature employs locally self-uniform networks for structural coloration.
• Elucidation of the origin of the champion photonic band gap found in diamond-like (3D) and honeycomb-like (2D) dielectric networks. This is a fundamental question in the photonic crystal research field, which has been unanswered for more than 25 years. Florescu commented, “Our formalism is finally able to answer this fundamental question with simple geometrical/topological metric without the need of electromagnetic simulations: the champion PBG structures correspond to network that maximize the local self-uniformity, namely strongly isotropic networks.”

Applications

The team believes that the project outputs will dramatically change the way artificial photonic materials are utilized and bring forward significant change in the field of photonic devices: light-weight photonic materials for integrated photonic-circuit architectures, as heat-rejecting window films and paints to improve the energy efficiency of buildings and vehicles, and biomimetic inspired applications including non-iridescent structural colouring.

Florescu commented, “The advantages of triamond-amorphous-enabled photonic devices include improved fabrication tolerance, layout flexibility, and isotropy, will provide a compelling case in the optical component and sub-system markets, and novel solutions for more energy- efficient materials.”

A related British patent (application no. 1601838.4) has been filed in the name of the University of Surrey, with contributing authors Steven Sellers and Marian Florescu recorded as the co-inventors. An international patent is currently also being pursued and University of Surrey is currently exploring exploitation in partnership with Etaphase Inc. to commercialize a new, substantially more compact, and more energy efficient structured material.

The project was funded by an IAA grant from University of Surrey (£9,600) and has leveraged funding from the EPSRC (United Kingdom) DTG Grant No. EP/J500562/1, EPSRC (United Kingdom) Strategic Equipment Grant No. EP/L02263X/1 (EP/M008576/1) (£1.9M) and EPSRC (United Kingdom) Grant EP/M027791/1 (£345K).