Scientists have developed an ultra-thin battery for smart contact lenses that can be charged with tears

Scientist Lee Seok Woo of the School of Electrical and Electronic Engineering at Nanyang Technological University said a scene from the movie «Mission Impossible» inspired his latest invention — batteries for smart contact lenses. In the fourth movie in the series, an agent wears contact lenses that can recognize faces and monitor eyes. Lee wanted to make this lens a reality.

Li realized that smart contact lenses would need safe and compact batteries, which would be crucial to the progressive development of these devices. Li and his team invented a battery that can be powered by a biocompatible saline solution as an alternative to lithium-ion batteries that contain flammable materials.

This new battery can be recharged using the conventional wired or chemical method. The battery is coated with glucose, and when it is immersed in saline, the glucose reacts with sodium and chloride ions to charge it. After an eight-hour chemical charge, the battery can reach 80% of its full capacity. It can then be used for a couple of hours during the day.

However, there is another unusual way to power the battery. You can use ordinary human tears for this purpose.

«Tear solution also contains glucose. This means that when you wear contact lenses, your tears can also charge the battery. If you cry more, you’ll be able to charge the battery more»,” said Lee.

Currently, the battery capacity and voltage are still very low. With the two methods, the battery can only produce a voltage of about 0.3-0.6 V. The standard voltage for a single AA battery is 1.5 V.

At this stage, this power is not enough to power the data storage or Internet connection, but the team is working on developing battery specifications.

The contact lenses themselves are extremely thin, 0.5 mm, so the size and flexibility of these batteries are key to preventing user discomfort.

«The thickness of our battery is about 0.2 mm, which is about twice the thickness of a human hair,» Li said.

He believes that once commercial production of such batteries is launched, their price will be only a few dollars.