Fur and Feathers: colour, structure and flow control

The objective in this exciting cross-disciplinary project is to investigate the potential of a bio-inspired coating of flexible devices to passively modify energetic modes of an unsteady crossflow and to assess, for the first time, the role of colour in determining mechanical properties. We seek an exceptional candidate with a strong first degree in physics, maths, engineering or bioengineering. The candidate should be keen to travel, spending at least 12 months in Melbourne, must have some prior programming experience and should be able to evidence the ability to work across disciplines.

This project will build on recent interest in the bioengineering field focused on understanding the underlying potential of bio-inspired surfaces for future engineering applications. The role of filamentous structures such as feathers or fur is of particular interest since they exist as both branched and unbranched forms, they are actively controlled by muscles, and their effects on flow are complex and understudied. Colour is known to have a direct impact on the mechanical properties of hairs and feathers, due to the structural role of melanin in the keratin strands that form them. In this way, colour is thought to directly affect structural endurance of the material, via UV resistance, but it has not been proven. Furthermore, ‘structural colour’ results from microscopic features which interfere with visible light, enabling them to reflect a far greater, sometimes iridescent, range of colours than would be possible from pigmentation alone. From a biological perspective this is interesting – which came first and why?

The coordinated response of arrays of fur/feathers to a flow instability is little understood, generally restricted either to the most simplified of scenarios or bulk analysis of more complex cases. The premise of this work is that a large group of flexible fibres to can be configured as a filter, with pre-determinable bulk properties. The hypothesis is the passive response of an array of fur/feathers can be made to either damp or amplify energy at selected frequencies. Furthermore, a smart inhomogeneous arrangement of such structures may be able to redistribute energy across multiple frequencies. The resulting surface would have important consequences for engineering applications where drag and noise reduction is paramount, or for energy harvesting devices designed to extract ambient energy. The parameter space of such a system is vast, and we navigate these dimensions by considering cases arising in nature, where conditions are clearly defined for given species. We will make use of existing data to categorise the structure of a range of filamentous structures for bird and mammal skin that are candidates for flow modification: (e.g. penguin/cormorant feathers; seal/beaver fur). We link engineering fluid dynamics with world-leading natural science research at both institutions, to explore animal locomotion and the link between the colour, form and structure of natural coatings, to find out whether there is a link between performance and colour.

Prof Richard Sandberg, Melbourne School of Engineering, The University of Melbourne

Dr Alistair Revell,The University of Manchester