These smart contacts can monitor the glucose in tears

Jet packs, flying cars, and smart contact lenses that monitor your health have all been better ideas than products. Now, a new study shows that at least smart contacts are getting closer to reality. Lenses with pliable, transparent electronics can measure glucose levels from tears in the eye—and warn wearers if they get too high. The lenses have been tested only in animals. But if they work in people, they could offer diabetics a pain-free way to monitor when and whether their glucose levels go out of whack, something that could send them tumbling into a coma, or worse.

So-called smart contact lenses were all the rage 4 years ago, as companies such as the Google spinoff Verily Life Sciences in San Francisco, California, touted future devices that could track glucose or even detect cancer. But then the problems set in: Early attempts used rigid and opaque electronics embedded into hard contact lenses, making them uncomfortable for wearers; the glucose measurements were also unreliable.

To tackle these problems, researchers led by Jihun Park, a materials scientist at the Ulsan National Institute of Science and Technology in South Korea, designed a set of components out of soft and flexible electronic materials that—wherever possible—were also transparent. They included two devices, an antenna and a rectifier, that capture radiofrequency signals from a nearby transmitter and convert them to a small amount of electricity. That charge powers a glucose sensor and a tiny green light-emitting diode (LED), which shines outward so it’s visible in a mirror but doesn’t interfere with the wearer’s vision. If the glucose sensor registers elevated levels, the LED turns off, warning a wearer that they may need to adjust their insulin levels.

The researchers weren’t able to make all of the components flexible, Park says. The glucose sensor, for example, contains two rigid pads of silicon. But to make the overall lens flexible, the scientists placed these rigid components on ultrathin “islands” for support, and then connected them to one another with a web of flexible wires so thin that they remain invisible to a wearer. These connected islands can move and stretch independently, in theory making the lens more comfortable. Park says the electronic components are so thin—only 1/100 the thickness of the soft contact into which they were incorporated—that a wearer shouldn’t notice them.

At least that’s the hope. Park’s team hasn’t tested its contacts in people yet. But rabbits wearing the lenses showed no signs of any adverse reactions, they report today in Science Advances. Park says the glucose sensors also accurately tracked levels of the sugar in the animals.

David Walt, a diagnostics expert at Harvard University’s Wyss Institute in Boston who was not affiliated with the work, says that the combination of flexible electronics and the novel LED readout “certainly is noteworthy.” However, he adds, smart contacts still have a way to go before they show up on pharmacy shelves. One issue, he notes, is that the glucose sensor relies on an enzyme, glucose oxidase, to bind to the sugar and measure its levels. But that binding generates hydrogen peroxide, a reactive compound that can damage the eye. And over time, the amount of glucose oxidase in the device will decline, he says, so researchers will need a way to continuously calibrate the amount of glucose the sensors are measuring.

Park agrees that future smart contacts will need to improve before patients can use them. And he won’t be alone in getting there. In addition to Verily, companies including Sensimed, EPGLMed, Samsung, Sony, and Apple are reportedly looking to launch smart contact lenses soon. For now, most are silent on the details. But if the new South Korean results are any indication, new wearable diagnostic contacts may be fast approaching.