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.
