Scientists develop an ultra-thin battery that can be charged with tears

Scientist Lee Seok-woo said a scene from the movie “Mission: Impossible” inspired his latest invention: smart contact lens batteries.

In the fourth film in the series, the agent wears contact lenses capable of facial recognition and eye tracking. Lee wanted to make that lens a reality.

“I was thinking, ‘How can I work in this field of smart contact lenses?’” the assistant professor at Nanyang Technological University’s School of Electrical and Electronic Engineering told CNBC’s “The Edge.”

Li’s experience with battery components served as a springboard for his entry into the field of wearable technology. He realized that smart contact lenses would need safe, built-in batteries, which would be essential to advance the development of these devices.

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

“Our battery is about 0.2 mm thick, which is about twice the thickness of a human hair,” Lee said.

Li and his team invented a battery that can be powered using a biocompatible salt solution as an alternative to lithium-ion batteries, which contain flammable materials.

This new battery can be charged using the traditional wiring method, or the chemical method. The battery is coated with glucose, and when dipped in a salt solution, the glucose reacts with sodium and chloride ions to charge it.

After eight hours of chemical charging, the battery can reach 80% of its full capacity. After that, it can be used for a few hours during the day.

However, there is another unusual way to operate the battery.

“The tear solution also contains glucose. This means that while you are wearing contact lenses, your tears can also charge the battery,” Lee said.

“If you cry more, you can charge your battery more.”

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

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

The potential partner he identified for me works in the healthcare field.

“We use glucose as biofuel. There are many diabetics who check their glucose level every day,” Lee said.

“We studied how we could detect the glucose level while the user was wearing contact lenses.”

Despite the potential prospects of such an innovation, Li believes that costs should be kept low, taking into account the capacity of the batteries.

“Once it is seriously commercialized, the battery should cost only a few dollars.”