A New Smart Contact Lens Can Charge Wirelessly Without Burning Your Eyeballs
The technology uses supercapacitors and will help speed the creation of contacts lenses that monitor the body
When smart contact lenses — wearable, functional electronics for your eyes — finally arrive, they could provide a revolutionary platform for biometric tracking, drug delivery, augmented reality, and military-grade night vision. But a major reason you can’t get these at your local Lenscrafters is because they require power to run, which may result in them becoming too hot. Anyone whose thighs have been seared by an overheated laptop would, understandably, think twice before sticking a potentially scorching disc of plastic, smart or not, onto their pupil.
However, a new collaboration between South Korean teams, led by Jang-Ung Park at Yonsei University in Seoul and Sang-Young Lee at the Ulsan Institute of Science and Technology in Ulsan, suggests a much cooler future for smart contact lenses.
The team, which published a paper last week in the journal Science Advances, says they’ve developed a soft, wirelessly recharging smart contact lens that didn’t sear the eyeballs of the male New Zealand white rabbit and the male human volunteer who wore one for 10 minutes straight.
That’s an impressive achievement for a wirelessly charging device. Electronics tend to get hot because inefficiencies in energy transfer and storage lead to heat being lost as waste. Park and Lee’s smart contact lens avoids that problem because it employs a form of energy storage called a supercapacitor instead of conventional lithium-ion batteries. (As Samsung learned with its exploding Galaxy Note 7 smartphones, lithium-ion batteries can store a lot of energy but are often rigid, big, and hot.)
Supercapacitors tend to have lower voltage limits than rechargeable batteries, but they can charge and discharge more quickly than lithium-ion batteries. That means they have a longer lifespan, which makes them ideal for a tiny, continuously running wireless device like a smart lens. Though supercapacitors can also emit heat and be bulky, the team discovered a clever workaround.
Using technique called microscale dispense printing, the team drew the components of the supercapacitor around the edge of the lens so it wouldn’t block the wearer’s vision. A millimeter-scale wireless transfer unit charged the supercapacitor while it was being worn, emitting enough energy to power an LED on the smart lens “without any external power transmitting facilities,” says David Ahn, a graduate student in the laboratory of co-author Lee.
The human test subject did not show any abnormal response.
The demo lens didn’t carry any of the sensors or monitors that functional smart contacts might carry in the future. The LED, illustrated by the Terminator-esque red light in the pupil of the volunteer below, was installed to demonstrate that the printed supercapacitor and the wireless charging system actually worked.
“The human test subject did not show any abnormal response,” Ahn says. “After wearing the lens, the human test subject did not show any signs of discomfort such as eye redness. Such results implied the possibilities of the practical use of the smart contact lens.”
Previous efforts to power smart lenses included using a flexible micro-battery, harvesting the kinetic energy of blinking, and tapping the chemical energy of human tears. Printed supercapacitors could be an elegant and safe solution, but now the team must figure out how to fit them — together with the components for wireless communication, extended use, and diagnostic sensors — onto a single lens.
“Miniaturization and compact integration of these high-performance devices in the limited area of the smart contact lens would be the key challenge,” Ahn says.
Supercapacitors can, in theory, power a variety of technologies on a smart contact lens. In 2014, scientists at Verily, Alphabet’s life science arm, attempted to measure glucose in tears with a smart lens project. That initiative was shut down in 2018 because of concerns that the glucose in tears didn’t accurately reflect the blood sugar levels in human blood — a life-or-death matter for diabetics. Augmented reality, another potential use for smart contact lenses, is likely an even more distant goal.