Photonic Structural Materials with Controlled Disorder

Project Information

PrISMoID

Grant agreement ID: 833895

DOI

10.3030/833895

Project closed

EC signature date 10 May 2019

Start date 1 September 2019

End date 31 May 2025

Funded under

• EXCELLENT SCIENCE - European Research Council (ERC)

Total cost

€ 2 499 990,00

EU contribution

€ 2 499 990,00

Coordinated by

UNIVERSITE DE FRIBOURG
Switzerland

Periodic Reporting for period 4 - PrISMoID (Photonic Structural Materials with Controlled Disorder)

Reporting period: 2024-03-01 to 2025-05-31

Summary of the context and overall objectives of the project

The way colour arises from materials is seemingly well understood. In most cases (both natural and manufactured), pigments absorb part of the optical spectrum. In nature, so-called 'structural colour' is also widespread. Rather than absorbing part of the optical spectrum visible to the human eye, light interference from 100-nm-scale structures separates the different optical dispersions in transmission and reflection. While this has been known for more than 100 years, there is still controversy about the requirements for these structures. Perfectly regular, periodic, transparent structures have a well-defined, brilliant colour signature ('optical band gap'), whereas disordered morphologies randomise the light paths through the material, resulting in the colour white.

Surprisingly, many organisms, such as many birds, produce a brilliant colour response from seemingly disordered morphologies made from transparent materials. From a physics point of view, these colours must also arise from interference between light waves within the material, which requires structural correlations. In other words, the coloured appearance of bird feathers is due to an interplay of order and disorder in their structure.

The aim of the PrISMoID project is to discover the rules underlying this interplay between order and disorder, provide a theoretical description of the phenomenon and develop manufacturing approaches to create coloured materials based on the discovered structural 'blueprint'.

The PrISMoID project will provide a new way to create colour. One approach being pursued is to create 'photonic pigments'. These are small spheres with an internal structure that is coloured through the order-disorder mechanisms described above. Since these can be made from any transparent material, they could replace brightly coloured 'traditional' pigments, which are often toxic or cause adverse health conditions.

The main objectives of PrISMoID are divided into four phases. The first phase involves establishing the experimental and theoretical techniques required for PrISMoID. This includes, in particular, acquiring and analysing 3D data on the sub-100 nm length scale. The second phase involves employing these techniques to analyse ordered and disordered photonic morphologies in various biological specimens, including animals and plants.

Work performed from the beginning of the project to the end of the period covered by the report and main results achieved so far

Two techniques focusing on the acquisition and analysis of 3D morphologies were developed. One of these involved the 'slice-and-view' methodology of focused-ion-beam scanning electron microscopy (FIB-SEM). This methodology was modified to enable the 3D imaging of porous organic networks with excellent resolution.

The initial experimental studies focused on beetles with differently coloured scales. The organisms studied featured scales with different colours and ordered and partially disordered morphologies. These studies enabled the first qualitative conclusions to be drawn about the role of disorder in the scales and their colour response.

The PrISMoID project employed the developed FIB/SEM methodology to examine organisms exhibiting various photonic morphologies. These results are currently descriptive in nature.
Two types of organisms were studied using the developed 3D imaging techniques: one with a 3D co-continuous network and one with colloidal packing.

The third phase of the project focused on manufacturing 'photonic pigments', which is a promising approach for the scalable implementation of the ERC-funded project's results. The first two publications covered the reproducible manufacture of photonic pigments based on block copolymer self-assembly. The project proceeded to optimise these additives to enhance colour brightness. Finally, we succeeded in formulating a photonic paint.

Numerical modelling of the photonic response to order-disorder interplay has also made substantial progress, with two publications in preparation. The project will continue beyond the end of PrISMoID.

Progress beyond the state of the art and expected potential impact (including the socio-economic impact and the wider societal implications of the project so far)

Significant progress has been made since the project began, in line with the original proposal and across the wider field. Technologically, the development of a robust slice-and-view method for acquiring 3D datasets of biological specimens with a voxel resolution of up to 10 nm was a breakthrough upon which the entire project is based. Results on the interplay of order and disorder have been published. One notable initial qualitative outcome is the identification of a structural motif present in all biological photonic specimens with network-like morphologies that have been studied. Nodes within these networks exhibit connectivity with four neighbours, forming a diamond-like local structure. This is surprising since such connectivity is difficult to achieve through self-assembly and self-organisation processes. Conversely, it is intriguing given that diamond morphologies are predicted to exhibit a complete photonic band gap, regardless of the viewing angle. While we are in the process of further analysing these results, we speculate that these morphologies are highly effective in creating a strong photonic response.

Further results include a new paradigm on the interplay between pigment absorption and structural colour in biological specimens. In terms of manufacturing, we have demonstrated a fully colour-tunable photonic pigment. It is interesting that it is possible to vary between order and disorder in these photonic spheres, which lies within the scope of PRiSMoID. Recently, we succeeded in formulating the world's first photonic paint.

Work is ongoing to develop a Monte Carlo-based approach to simulate the effect of order-disorder interplay on photonic material properties. The aim is to classify the order-disorder interplay into order parameter ranges for which photonic colour is obtained and compare them with those where it is absent.

PRiSMoID has triggered several new research projects that will build on its work. Within the framework of two SNSF grants (SPARK and Ambizione), we are designing water-based membrane systems that self-organise into ordered co-continuous phases, which can then be solidified and dried to produce photonic materials. This approach directly mimics the metamorphosis process in butterflies.

Our project on creating photonic pigments and paints is ongoing. We are developing this project into a scalable technology and improving the optical appearance of the photonic pigments. Finally, we are pursuing a strategy for 'switchable' photonic colour.

Inspired by our observations of colourful beetles, we are developing a colloidal approach that mimics the order-disorder interplay found in these organisms. To this end, we disrupt the otherwise ordered self-organisation of colloids to create non-iridescent colour in a scalable fashion. This concept has been recognised by the award of a 'Sinergia' grant from the Swiss National Science Foundation

By collaborating with a new partner, we are further developing this concept to create colourful, non-close-packed colloidal assemblies.

In summary, the PRiSMoID project has substantially enhanced our understanding of how structural colour is produced by non-periodic network assemblies. Through studying biological specimens, we have identified important underlying mechanisms and developed models and numerical schemes that replicate these mechanisms. We are also creating scalable approaches for their technological implementation.

beetles.jpg

Analysis of the red and blue coloured scales of the Pachyrhynchus congestus mirabilis weevil