We have projects in the development of new materials for prosthetics and coatings for body implants which improve their performance in the body. A current focus is the development of a bio-compatible coating to increase the wear resistance of a new synthetic heart pump.

> New Materials for Prosthetics

This work is done in collaboration with the University of New South Wales (Professor C.R. Howlett and Dr H. Zreiquat). We have support from the ARC to develop materials and systems for recruiting bone cells and promoting their growth on artificial surfaces. This development will reduce the hospitalization time of patients requiring skeletal or joint repair following fracture or injury. We plan a new project to investigate the feasibility of seeded trenches produced by lithographic methods for selective recruitment of bone cells.

> Bio-compatible Wear Resistant Coatings

This work is supported by the ARC SPIRT scheme and is a joint venture between the University of Sydney (Professors D.R. McKenzie, M.V. Swain and Mr R. Tarrant) and Ventrassist, a development company (Dr. N. James). We are developing low friction coatings with high bio-compatibility based on carbon. The challenge is to produce coatings with extreme levels of adhesion which are also thick. These coatings play a vital role in the new Ventrassist heart replacement pump.

> Bio-Optics

The living world provides a multitude of examples of the clever use of light for vision camouflage, courtship and signalling. The research is part of a collaborative program between Professor D. R. McKenzie of the University of Sydney, Dr Maryanne Large, and Dr Andrew Parker originally from the Australian Museum in Sydney. Of particular interest is the use of structure to achieve reflections and colour effects, as an alternative to pigmentation. Structural colours are produced by such processes as scattering, interference effects and diffraction. These mechanisms can be found in many natural systems and seem to be particularly important in marine organisms, because their high reflectivity means that they can function efficiently in low light levels. Publications of the Bio-Optics group discuss the use of broad-band reflectors and the use of laminar structures. Randomness or "chaotic" structures are used in clever ways to produce effects which are difficult, even today, to reproduce by artificial means.

The Secret Light of Beetles: The "metallic" reflectors in Christmas beetles are composed of multiple layers of high and low refractive index materials, with randomised spacings. This gives a high reflectance over a broad spectral range- a method also employed in the shiny skin of fish. These may be used in conjunction with scattering or thin film effects.

Christmas beetles (left) and SEM of a cross section through the cuticle of a beetle (right).

For further information on any of the above research fields, please contact Prof. David McKenzie, d.mckenzie@physics.usyd.edu.au.