Blue is often described as the rarest colour in natural organisms. Elucidating the underlying colour mechanism(s) is always very impactful for the understanding of the natural world. In this research, the colour of the blue rounded spots occuring in the skin of Taeniura lymma stingray was unveiled by a combination of experimental and numerical techniques. Our results demonstrated that this blue colour arises from coherent scattering in quasi-ordered photonic structures occuring in the skin of this stingray. These structures made of collagen fibers are mostly unknown in marine species. In addition, structural blue colours had never been reported in elasmobranches.

Every year, billions of birds collide with windows, often resulting in their death, as well as in significant material damage. However, many animal species have developed photonic structures active in the UV due to their perception of light in this wavelength range. These structures allow us to elaborate new optimised coatings for selective UV reflection through a bioinspiration approach. These bioinspired coatings consist of a periodic multilayer of metal oxide layers deposited on soda-lime glass with patterns. The optical response of the multilayers was numerically optimised in terms of morphology and material composition using human and avian colour perception models.