Soft smart lenses detect blood sugar levels

Konstantin Sheiko
January 30, 2018

‘Smart’ devices and gadgets are supposed to make our lives easier, but unfortunately, this isn’t always the case. The so-called ‘smart contact lenses’ made the news four 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, only to fail miserably. The performance-related problems set in - early attempts used rigid and opaque electronics embedded into hard contact lenses, making them uncomfortable for wearers. 

Besides, the glucose measurements were also unreliable. Tackling 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 it was possible, were also transparent. They included two devices, an antenna, and a rectifier, that capture radiofrequency signals from a nearby transmitter, converting them to a small amount of electricity. 

The accumulated charge powers a glucose sensor and a tiny green light-emitting diode (LED), which shines outward, so it is visible in a mirror but does not interfere with the wearer’s vision. If the glucose sensor registers elevated levels, the LED turns off, sending a warning to the user that the insulin levels might have to be adjusted.

According to Park, the researchers could not create the lenses entirely consisting of soft components. The glucose sensor, for example, consists of two hard pads of silicon. In order 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 really thin, comprising only 1/100 the thickness of the soft contact into which they were incorporated, and that in theory, a wearer should not notice them.

At least that is the hope. Park’s team has not tested its contacts in people yet. But rabbits wearing the lenses showed no signs of any adverse reactions. Park says the glucose sensors also accurately tracked levels of the sugar in the animals.

Diagnostics experts that are not affiliated with the work comment that the combination of flexible electronics and the novel LED readout “certainly is noteworthy.” However, they also insist that smart contacts still have a way to go before they show up on pharmacy shelves.

For example, the glucose sensor in the lenses 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, 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. However, the benefits of having a pair of such lenses are obvious for any diabetic person today. Among them keeping blood sugar levels optimal all day, avoiding spikes or lulls during sleep – because of the lenses, these everyday problems would not depend on pure luck anymore. You could also forget about pricking your finger several times each day.

But when and how will diabetes patients be able to get their hands on this technology? Lenses with pliable, transparent electronics can measure glucose levels from tears in the eye, warning wearers if they get too high. If the lenses work in people, they could offer diabetics a pain-free way to monitor when and whether their glucose levels go out of control, something that could send them tumbling into a coma, or worse. 

If the new South Korean results are any indication, new wearable diagnostic contacts may be fast approaching. In addition, 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.