Researchers have developed a method for creating a complex structure previously found only in nature, which will allow them to manipulate and control light in new ways.
According to new research by scientists at the University of Birmingham, the structure, which naturally exists in the wing scales of some species of butterfly, can function as a photonic crystal. It can be used to regulate light in the visible range of the spectrum, as well as for lasers, sensors, and solar energy harvesting devices.
Their computational study, which was published in the journal Advanced Materials, shows that the complex gyroid structure can be self-assembled from designer colloidal particles hundreds of nanometers in size.
The gyroid is commonly referred to as a curved surface that divides space into two interwoven channels. Each of these channels can be represented by a network of linked vertices with three-fold connectivity that corkscrews through space in one of two directions, right or left.
This twist makes each network chiral, which means that mirror images, like left and right hands, cannot be superimposed on each other. This is significant because chirality gives a photonic crystal additional optical properties.
When two networks of opposite handedness are joined in the form of a double gyroid structure, the chirality is lost. This happens in some synthetic systems.
The investigators present a single network gyroid structure made of colloidal spheres as a target for self-assembly—nature’s way of building architectures—before creating the design principles for manufacturing this chiral crystalline structure in computer simulations.
This is a new and exciting way to fabricate nanophotonic media with exceptional and tailored chiro-optical properties, with immense control over their properties.
Dr. Angela Demetriadou, Study Co-Author, School of Physics and Astronomy
So far, diamond structures have received the most attention in the field of self-assembling colloidal photonic crystals. Colloidal diamond self-assembly presents several challenges, including the requirement to choose the cubic form over its hexagonal counterpart for practical applications as photonic crystals in optical devices.
The novel approach developed employs patchy spheres with a designer-decorated surface to encode the information of the target structure—the single colloidal gyroid. The surface decorations are sticky, attracting particles to form the network structure.
Furthermore, the work demonstrates that the single colloidal gyroid has intriguing optical properties due to its chirality, which is lacking in a diamond structure.
To the best of our knowledge, this is the first report of direct self-assembly of single colloidal gyroid structures from designer building blocks. We hope that our novel approach will stimulate further investigations in the field of colloidal self-assembly, especially experimental efforts to build on this exciting development.
Dr. Dwaipayan Chakrabarti, Study Corresponding Author, School of Chemistry, University of Birmingham
This expectation is shared by Professor Stefano Sacanna, a New York University Professor with world-leading expertise in colloidal synthesis and self-assembly of new materials which is not involved in this study.
With their work, Chakrabarti and co-workers bring an exciting new target to the attention of the colloidal self-assembly community. Using just spheres with a clever patchy design, their bottom-up routes to colloidal gyroid structures pave the way for a new generation of experimentally achievable photonic crystals.
Stefano Sacanna, Professor, New York University
Flavell, W., et al. (2023) Programmed Self-Assembly of Single Colloidal Gyroid for Chiral Photonic Crystals. Advanced Materials. doi.org/10.1002/adma.202211197.