The February 2023 issue of IEEE Spectrum is here!

Close bar

Spider Silk Sensors Could Search for Life on Mars

Optical fibers made from silk could detect chemicals

2 min read
Spider Silk Sensors Could Search for Life on Mars
Photo: Luc Thevanaz/EPFL

Ziggy Stardust would love this: Spiders could help find life on Mars.

That is, optical sensors made with spider silk could be used to look for trace gases produced by biological processes, according to a researcher who showed how silk could be used in place of conventional optical fibers, under a grant from the European Space Agency. The scientists hunting for life on Mars would like to be able to test for small amounts of ammonia, which might be emitted by the metabolism of microbes, so they need a sensor that can detect that while remaining insensitive to the large amounts of carbon dioxide in the Martian atmosphere.

Spider silk does the trick, says Luc Thévanaz, who heads a research group studying fiber optics and optical sensing at Swiss Federal Institute of Technology of Lausanne. The fiber can carry a beam of light, and when something in the environment affects the fiber, that alters some characteristic of the light beam. The concept is used in strain sensing for bridges and other large structures: If the fiber stretches, it changes the spacing of an optical grating inside, altering the wavelength of the light passing through and alerting monitors to the amount of strain.

But conventional optical fibers, made of silica glass, are chemically inert, making them poor chemical sensors. On the other hand, Thévanaz says, “the optical properties of the silk are massively modified by chemicals.” The presence of certain molecules causes hydrogen bonds in the silk molecules to break, and the result is a change in the polarization of light passing through. This only works, though, on polar molecules, such as ammonia, which have unequal charges on each end. Non-polar molecules, such as CO2, cause no response.

Thévanaz and his team tested their concept using the silk dragline from a female Nephila edulis spider. They found they could get good light transmission from the visible to the infrared, up to wavelengths of about 1400 nm. Their best transmission was infrared light at 900 nm, which had optical loss of 4 dB/cm, a measure of how far the light can travel before being absorbed by the material. While that’s orders of magnitude higher than the loss in silica, which can be as low as 0.2 dB/km, it’s sufficient for sensing applications. “Silk is extremely transparent, though far less transparent than glass,” Thévanaz says. “Loss is not a big problem because over a few centimeters we have an extremely sensitive response.”

For more down-to-earth applications, these silk fiber sensors might be useful for monitoring industrial processes or as sensors in automobiles, because they shouldn’t need to be periodically replaced like sensors that rely on irreversible chemical reactions, Thévanaz says. He’s hoping to build up a library of measurements showing which changes in the light beam correspond to particular chemicals. And he says the process can be improved with the use of artificial silk, or by doping the silk with other chemicals to alter what it’s sensitive to.

The Conversation (0)

Two Startups Are Bringing Fiber to the Processor

Avicena’s blue microLEDs are the dark horse in a race with Ayar Labs’ laser-based system

5 min read
Diffuse blue light shines from a patterned surface through a ring. A blue cable leads away from it.

Avicena’s microLED chiplets could one day link all the CPUs in a computer cluster together.

Avicena

If a CPU in Seoul sends a byte of data to a processor in Prague, the information covers most of the distance as light, zipping along with no resistance. But put both those processors on the same motherboard, and they’ll need to communicate over energy-sapping copper, which slow the communication speeds possible within computers. Two Silicon Valley startups, Avicena and Ayar Labs, are doing something about that longstanding limit. If they succeed in their attempts to finally bring optical fiber all the way to the processor, it might not just accelerate computing—it might also remake it.

Both companies are developing fiber-connected chiplets, small chips meant to share a high-bandwidth connection with CPUs and other data-hungry silicon in a shared package. They are each ramping up production in 2023, though it may be a couple of years before we see a computer on the market with either product.

Keep Reading ↓Show less