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EPFL Team Uses Spider Silk to Identify Molecules

Fiber optics specialists at EPFL have discovered some distinctive qualities of spider silk in relation to reactions with specific substances and conducting light.

Luc Thévenaz, professor in charge of EPFL's Group for Fiber Optics, decided to build upon an idea suggested by the European Space Agency. Instead of focusing on traditional fibers developed from glass, he concentrated on the strands of silk produced by spiders for their webs.

These silk strands have characteristics that are similar to fibers made from glass. The strands are smooth, cylindrical in shape, solid, and transparent. Though when compared with glass that is inert, spider silk seems to be developed from extremely long proteins that are rolled to form a helix structure, comprising bonds that are sensitive to many chemical substances.

The helix in the silk strands unwinds whenever polar molecules like acetic acid and ammonia come into contact with its bonds. This measurably modifies the way the strands conduct light, and it gave us the idea of using them to make chemical sensors.

Luc Thévenaz, Professor, EPFL's Group for Fiber Optics

The fiber optics specialists discovered that changes occurring in the helix structure were totally reversible, and this property allows repeated usage of sensors using spider silk.

We are looking at the possibility of creating silks by adding molecules meant to react with the substances to be tested. That is often impossible with glass fibers, which we have to heat to more than 1,000°C in order to stretch.

Luc Thévenaz, Professor, EPFL's Group for Fiber Optics

The biodegradable property of silk allows it to be used for sensors, permanently implanted in a living body.

Doctoral student Desmond Chow and post-doc Kenny Hey Tow, from EPFL, are currently working with natural silk strands that are 5 microns in diameter. These strands were obtained from Australian Nephila edulis spiders, grown at the Zoology Department of the University of Oxford.

A silk strand is stretched into a small bracket and then a laser beam is directed at one end of the silk strand. Infinitesimal changes occurring in the light passing through the other end are measured using a polarization analyzer.

Currently, this research is in its developing stage and is actually enhancing the imagination of Dr. Thévenaz.

We have presented it at several conferences, where it was met with significant interest,” he said. In the meantime, the study is hoping to receive research funds. “We are entering a totally new domain that has yet to be explored.

Luc Thévenaz, Professor, EPFL's Group for Fiber Optics

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