Spider Silk Sheds Light on Future of Optical Fibers
A scanning electron microscope image of a light circuit made with silk threads. The circles are disks made of a synthetic material. The thin lines are single threads of silk.
CREDIT: Image courtesy of Nolwenn Huby
A new technology sounds a little like it could have come from a fairy tale. Researchers have found a way to direct light along strands of spider silk, running light through tiny silk versions of the glass or plastic optical fibers that are used in telecommunications and in optical fiber flowers.
"We managed to propagate light in spider silk," said Nolwenn Huby, a physicist at the University of Rennes in France who worked on the silk optical fibers. "We also managed to incorporate this pristine silk into an electronic chip."
The pristine, or unprocessed, spider silk isn't as efficient a carrier of light as glass and plastic cables. But Huby's research team, which included physicists and chemists from France and Canada, is interested in developing silk optic fibers because of their potential use in medical devices and sensors. Because silk is a biologically made product, the body is less likely to reject silk-based devices that are embedded in the body, Huby said. Silk strands are also very thin, about a tenth of the thickness of a human hair, so they could go into cameras designed to be threaded into the body. Current internal cameras use glass optical fibers, which are thicker.
Huby said her team's experiments are the first to show that silk is able to carry light from one location to another. They created a microchip with round disks on it that were made of a synthetic material. Between each disk sat a single, short piece of silk. When they injected laser light into one of the disks, they saw that the light runs between the disks, inside the silk, instead of diffusing away.
Although the composition of silk and glass differ, the physics of how light acts when it runs inside those materials is the same, Huby said. The light undergoes total internal reflection, reflecting in a zigzag pattern down the silk or glass strand without escaping into the surrounding air.
The bits of silk thread Huby and her colleagues tested are very short, just centimeters long, so spider silk won't be replacing network cables, Huby said. Short lengths work fine for small medical devices, however, she said. [SEE ALSO: Vanishing Electronics: Safer Medical Implants, Less Trash]
Next, the team will try to improve the amount of light silk is able to carry. One way they'll do this is to try to straighten the silk fibers, which naturally bend slightly. They'll also envelop the silk in different materials to try to alter the way it carries light. "I think we will first start to work in liquid, like in water, for example," Huby said. "We have lots of experiments to do to understand and control the optical propagation in the silk."
The chemists and physicists will also be asking biologists what kind of sensors they'll want. "It depends on what the biologists will say and will see in this material," Huby said.
She and her team presented their work yesterday (Oct. 15) during the annual meeting of the Optical Society in Rochester, N.Y.