Web of light

October 2004

One of nature's most remarkable materials -- the dragline silk from the golden orb-weaver spider -- is stronger than steel and has great commercial potential. The challenge has been to understand its molecular structure. Penny Fannin reports on a Monash physicist who is using synchrotron radiation to help expose the structure of spider silk.

Materials researchers have long wanted to unravel the structure of spider silk. Its strength and elasticity make it a good candidate for a broad range of medical and industrial applications, including artificial tendons and ligaments, sutures for ophthalmic and micro surgery, biodegradable fishing lines and bulletproof vests. But such developments have been hindered as the detailed molecular structure responsible for spider silk's unique properties has eluded researchers.

Fine research: Dr Andrei Nikulin is using synchrotron technology to expose the structure of spider silk. Photo: Greg Ford

This is partly because the silk threads are so fine -- down to the level of microns (a micron is a thousandth of a millimetre) -- that their structure cannot be viewed with visible light. While electron microscopes could be used to analyse silk samples, this requires that the samples be destroyed. The only non-destructive way of revealing how the molecules within spider silk are assembled is to use X-rays.

This is where Monash physicist Dr Andrei Nikulin comes in. Dr Nikulin, a senior lecturer in the School of Physics and Materials Engineering, is using the X-ray radiation produced by synchrotrons to determine the structure of nylon fibres with the aim of applying the knowledge gained to spider silk.

Synchrotrons are large particle accelerators that create bright, pinpoint beams of light. These high-intensity light beams allow scientists to examine the structure of matter down to the level of atoms. The Australian Synchrotron, being built at Monash University's Clayton campus, is expected to be completed in 2007.

Dr Nikulin is using the Spring-8 and Photon Factory synchrotrons in Japan to examine the structure of crystalline nylon fibres.

He has been developing a technique for analysing the interaction of X-rays with solid surfaces to provide detail of the structure of crystals down to the atomic level. Further, he has designed software to analyse data on the intensity of scattered X-rays, thus revealing new information on the structure of materials.

Although Dr Nikulin has been testing his method on nylon fibres, he has recently started collaborating with Associate Professor David Grubb from Cornell University in the US, in preparation for using synchrotron radiation to examine the structure of artificial spider silk.

"With spider silk it's not enough just to see a flat image; you need a cross-section of the material at high resolution -- a diameter of one micron or less," Dr Nikulin says.

Past experiments using mechanical testing, nuclear magnetic resonance and X-ray scattering have shown that the dragline silk of the golden orb-weaver spider is similar to nylon fibres.

"What I'm doing with the nylon experiments is proof-of-concept. I want to be sure that the method I have developed for determining the structure of materials can be accurately applied to nylon fibres before we attempt to analyse spider silk."

Earlier this year Dr Nikulin and Professor Barry Muddle, also from the School of Physics and Materials Engineering, received a $570,000 Australian Research Council grant to further develop Dr Nikulin's method of analysis. Now that the method has been established for crystalline structures, it is being applied to nanoscale interfaces such as those between two metals.

Manufacturers across a range of industries, from automotive to aviation, develop nanoscale products that involve interfaces such as metal/metal or polymer/metal. Sometimes the products fail but are so tiny that it is not immediately clear why.

Action

For more information on the Australian Synchrotron, visit www.monash.edu.au/synchrotron/. Dr Andrei Nikulin can be contacted on +61 3 9905 1353 or email andrei.nikulin@spme.monash.edu.au.