Smartphone displays smart enough to sense your spit. Seriously

Researchers are working on glass that could detect fluids simply through contact, which may hold medical benefits.

A laser writes an invisible waveguide into a smartphone's display glass. Optics Express

Wondering if you have a cold? You may be able one day soon to spit on your smartphone to find out.

Researchers at Polytechnique Montréal in Canada, collaborating with glass maker Corning, are getting closer to making that kind of feature a reality for mobile devices by developing a "smart" glass that can analyze fluids on its surface.

Disgusting? Maybe. But such a capability may allow smartphones, wearables and tablets to expand their usefulness in personal medicine, security, and food and environmental safety. Such features could be indispensable for a mobile-devices industry fixated on playing a bigger role in health and fitness. Apple, Samsung and others have been rolling out a bevy of health-related apps, fitness-focused smartphones and wearables that track sleep cycles and steps walked.

The researchers say the glass could significantly push forward mobile-health offerings, enabling devices to assess pathogens in spit to diagnose an illness or test blood sugar levels in blood for diabetic patients. More broadly, the material could also be used to gauge carbon-monoxide levels in the air or offer an added security layer embedded in the display glass -- just to name a few ideas.

For Corning, this could be a breakthrough product, something the company would badly need if it were to lose Apple as a customer. The technology giant is rumored to be switching to sapphire glass and away from Corning's own durable Gorilla Glass for its iPhone displays, threatening Corning's position as the go-to display company. However, the smart-glass technology remains in the research phase and is likely years away from reaching the market, if it makes it at all, Corning said.

Catching the right waves

The next-generation feature is based on a type of technology that's been around for about 20 years, but only recently has been gaining attention. Researchers have known for a while they can shoot lasers into glass to create tiny embedded pathways -- called waveguides -- that can be used to transmit information using tiny beams of light.

While holding plenty of potential, this type of technology has been slow to progress. Waveguides made in labs so far leak out too much light to work properly.

The Polytechnique and Corning researchers believe they made a substantial step forward in solving the leakage problem. They developed waveguides within Corning's Gorilla Glass that are 10 times better at reducing light leakage than what has previously been created. That achievement elicited a "hallelujah" moment for the team, said Polytechnique researcher Jerome Lapointe, after testing many other kinds of glass. The study's results were published last month in the Optical Society's Optics Express journal.

The technology still needs work, but the question remains whether electronics makers have any interest in the first place in adding waveguides to their mobile devices -- not to mention whether people can be convinced to spit on their phones.

"We're just at the beginning," said Alan Evans, an optical-physics research director at Corning. "We can dream up all this stuff, but we need that market confirmation to say, 'Yup, that really does solve a problem.'"

Laser meets glass

The researchers used a short-pulse laser, called a femtosecond laser, to create waveguides inside the Gorilla Glass that were so small they're invisible to the naked eye. They then used other, tiny lasers to shoot beams of light through these pathways -- similar to an electric current passing through a metal wire -- to create sensors. The Gorilla Glass ended up with few internal cracks and imperfections after being shot with the femtosecond laser, making it particularly good at channeling the light.

Making waveguides. Optics Express

The team developed two types of mobile tools using waveguides: a temperature sensor and an authentication system. The temperature sensor, using a straight and curved waveguide, measured a person's temperature or the temperature of whatever the glass was touching. The authentication system was essentially Morse code written on the glass that could then be read using an infrared camera. Such a code could be unique to every phone, providing an added layer of security for devices.

Those tools are still rather basic, but could provide the building blocks to make more complex waveguides. That would potentially allow devices to analyze fluids on their display surfaces or measure other things around them, Corning's Evans said. "It's not science fiction. It's certainly conceivable," Evans said about such complex sensors. "It's still in research but we can see a path."

In addition to adding new functions to mobile devices, waveguides could also be a route to making see-through electronics, like a computer on a window pane -- a concept also being pursued by a number of researchers and companies using a variety of other technologies.

Potential boon for Corning

If waveguides catch on, the benefits for Corning could be huge. The 163-year-old company based in Corning, NY -- which makes glass used in smartphones, televisions, and lab equipment -- has been successful selling its Gorilla Glass, which has been used as a cover glass for more than 2.7 billion devices worldwide.

More recently, sapphire glass -- a harder material made of purified aluminum oxide used for high-end watch faces, camera lenses and LED lighting -- has threatened Corning's position as a top electronics-glass supplier. Device makers are weighing the benefits of using sapphire. Apple is rumored to be considering switching from Gorilla Glass in its highly anticipated iPhone 6 to sapphire glass, which is offered by companies including GT Advanced Technologies and Kyocera. Corning has publicly criticized sapphire glass, saying the rival material is heavier, more expensive to make and doesn't hold up well for smartphones.

The potentially good news for Corning is that sapphire glass seems to be a lousy conduit for waveguides, since its crystalline structure makes it difficult to write pathways without cracking the material.

Corning said Apple "remains a valued customer," noting that it has supplied Gorilla Glass to the tech giant since the iPhone was introduced in 2007. It plans to unveil a new generation of Gorilla Glass later this year.

Apple didn't respond to a request for comment.

"This Gorilla Glass could survive longer if it is integrated into some other kind of functionality on your mobile phone," said Saulius Juodkazis, a nanophotonics professor in Australia who coordinated the Optical Society's review of the study. He wasn't involved in the research. "Gorilla Glass could have a strong future."

He said more research was needed to fully understand what makes Gorilla Glass good for making waveguides. Juodkazis added that new glass materials are constantly coming out from different companies, so it's possible other types of glass are useful for making waveguides, as well.

Plenty more needs to be studied. In the meantime, Lapointe and his fellow researchers are working on patenting the temperature sensor and authentication system, and they're looking for industry partners to continue developing the technology. With a focused effort, there's a chance those two tools could be integrated into smartphones within a year. "We are at the point where people are starting to care about it," said Evans, of Corning," and potentially pay money for it."