A battery for smart contact lenses has been developed. He feeds on tears

Although various companies are working on smart contact lenses, they are still far from being commercially available. One of the key problems lies in the need to power the device that is applied to the eyeball. The lens should remain thin, but still have a battery that will keep the electronics running throughout the day. Moreover, this battery must be recharged somehow. Scientists from South Korea came up with a potential solution that will be safe on the eye.

Current solutions predominantly rely on metal electrodes or inductive charging coils, sort of like wireless charging mats. Both options can be dangerous to the eye if the lens material breaks and the metal comes into contact with the eye. An alternative development of Korean scientists is an ultra-thin battery that is charged with tear fluid.

Such a soft battery with a thickness of 0.5 mm is built into the lens. It contains water and the enzyme glucose oxidase. When a flat, flexible battery is immersed in the tear fluid that covers the eye, the enzyme reacts with the sodium and chloride ions in that fluid, generating an electrical charge in the battery's water.

In laboratory tests carried out on a model of the human eye, the battery was able to deliver a current of 45 mA and a maximum power of 201 mW, which, according to scientists, will be enough to wirelessly transmit data from a smart contact lens for at least 12 hours. In its current form, the battery can withstand up to 200 charge/discharge cycles. In comparison, similar lithium-ion batteries typically last between 300 and 500 cycles.

Using such a contact lens will not be more difficult than usual. At night, it will “recharge” in a glucose solution, and during the day there will be enough tear fluid to ensure work.

There is no talk about a possible application in commercial smart contact lenses: the development has not yet been tested on humans.