Silk is strong – it can be stretched between 30 and 40 percent of its length before breaking, and has a tensile strength comparable to steel. It's been used in clothing for its softness and warmth. Now studies have found it can be used as fiber optic cable as well as sensors for biomedical devices.
Medical devices need data transmission but until now were confined to copper wires or actual glass fiber. Neither is particularly compatible with human tissue, though, and any medical device can cause irritation or infection. If they could be made of materials that were more like the human body, these kinds of problems could be reduced. On top of that, silk can eventually dissolve and be absorbed into the body.
Experiments done by Nolwenn Huby of the Institut de Physique de Rennes and Fiorenzo Omenetto of Tufts University have explored the optical properties of silk, and how to use them to build implantable electronics.
Spiders and silkworms both make silk. The fibers are a fraction of the thickness of human hair, only about 5 micrometers across. Huby's experiment involved taking spider silk fibers and attaching them to disc-shaped "reservoirs" which guide long-wavelength light (in the near-infrared) to the fiber. They found the light transmitted well enough that it could be used to send data. "Spiders can generate seven kinds of silk," Huby told Discovery News. "We use the kind used in making the web." (Other kinds of silk are used for wrapping up prey when caught or to trap it in the web).
More to the point, both silkworms and spiders make silk that is the same diameter through its whole length. Optical fibers have to be manufactured precisely, and making them that small is difficult and expensive. Silk would be cheaper, and can be made as long as the spiders are able to produce it. Silkworms can also be genetically engineered t produce spider silks.
Meanwhile, Omenetto's work focused on making silk-based polymers, taking advantage of the fact that silk is made up of proteins that can be absorbed back into the body over time. Since silk transmits light in a way similar to expensive plastics, it could be used to build sensors that could be implanted, and then allowed to dissolve.
Both Huby and Omenetto are presenting their work at this week's Optical Society of (OSA) meeting in Rochester, N.Y.
This isn't unlike the work done recently by John Rogers and his colleagues at the University of Illinois. His team is also working on electronics that dissolve in the body. Though Rogers' designs also involve silk as a covering his technique uses silicon and magnesium built with nanometer-sized pores.
Science fiction has usually portrayed the merger of people and machines as a permanent condition. If these studies pan out we may be looking at a future in which everyone is a cyborg for a little while.
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