Scientists are one step closer to making smart contact lenses a reality

A scientist from Nanyang Technological University Singapore holds up a NTU battery-infused smart contact lens. Scientists have created a flexible battery as thin as a human cornea that could potentially power smart contact lenses in the future. (Photo Courtesy of NTU's School of Electrical and Electronic Engineering)

Scientists have created a flexible battery as thin as a human cornea that could potentially power smart contact lenses in the future.

Researchers from Nanyang Technological University in Singapore shared the findings in a study published to the Nano Energy journal in June.

The high-tech contact lenses would include elements of augmented reality by showing information on the eye’s cornea.

The study revealed that, unlike rechargeable batteries like lithium-ion batteries that rely on wires and induction coils, metals unsafe for the use of a human eye, the 0.5 millimetres-thin NTU battery is made of "biocompatible materials" that do not contain wires or toxic metals.

The newly-developed battery has "glucose-based coating" that creates current when the saline solution’s sodium and chloride ions touch it. The battery’s water serves as the ‘wire’ for electricity to power up, the study said.

"Previous techniques for lens batteries were not perfect as one side of the battery electrode was charged and the other was not. Our approach can charge both electrodes of a battery through a unique combination of enzymatic reaction and self-reduction reaction," said the study’s lead author, professor Lee Seok Woo, in a news release.

According to the study, human tears can also power the battery because they contain sodium and potassium ions at a lower concentration.

Researchers tested a human tear solution on the battery and found that the battery’s life extended an additional hour for every 12-hour wearing cycle.

With a stimulated human eye, researchers discovered that the battery generates electrical power by reacting to the basal tears — the tears that create a thin film over our eyeballs — in a process called reduction.

In this study’s case, the battery could produce a current of 45 microamperes and a maximum of 201 microwatts power — enough to power a smart contact lens.

"By combining the battery and biofuel cell into a single component, the battery can charge itself without the need for additional space for wired or wireless components. Furthermore, the electrodes placed at the outer side of the contact lens ensures that the vision of the eye cannot be obstructed," said co-author Li Zongkang in the news release.

Lab tests also showed that the battery could be charged and discharged up to 200 times, close to lithium-ion batteries that have a 300 to 500-time charging cycle lifespan.

Researchers recommended the battery be placed in a solution that contains high levels of glucose, sodium and potassium ions for a minimum of eight hours while the user is asleep.

The battery can also be charged conventionally by an external power supply, the study noted.

"The smart contact lenses industry has been looking for a thin, biocompatible battery that does not contain heavy metals, and this invention could help further their development to meet some unmet needs of the industry," said biomedical and nanoscale optics specialist Murukeshan Vadakke Matham in the news release.

The study’s researchers say current uses for the smart lenses can be correcting vision, monitoring users’ health, as well as flagging and treating diseases for those who have chronic health conditions like diabetes and glaucoma.

For future uses, they say the smart lenses would be able to record and transmit everything the user sees and hears to a cloud-based data storage.

The researchers say they are conducting further research to improve the amount of electrical current the battery can discharge, and are working towards commercializing this invention by teaming with contact lens companies.