A battery charged by your tears may make smart contact lenses a reality

A thin battery inside a contact lens.
A thin battery inside a contact lens.

Smart contact lenses may have taken a step closer to becoming reality with the invention of a wafer-thin battery with a highly unusual way of recharging. The battery is just 0.2mm thick, or twice the width of a strand of hair, so it fits inside a standard contact lens that measures around 0.5mm thick. The thin profile means it won’t interfere with comfort or fit, and it will have the ability to recharge using your tears.

The battery is the work of Lee Seok Woo, a scientist and associate professor at Nanyang Technological University’s School of Electrical and electronic Engineering in Singapore, who was apparently inspired to start the project by the smart contact lenses imagined in the Mission: Impossible – Ghost Protocol movie from 2011.

But it’s not just an incredibly slim battery cell that makes us all tingly at the prospect — it’s the way it’s powered and recharged that gets us properly excited. Lee told CNBC the battery is powered using a “biocompatible saline solution,” rather than it being a lithium-ion cell like the ones in phones and smartwatches, as this would be unsafe for a product like a contact lens. Although the battery can be recharged using wires, just like normal batteries, a glucose coating around the lens reacts when it is submerged in a saline solution, causing it to charge up. Anyone who wears contact lenses now will be familiar with the process of storing lenses this way already, and it appears a similar method could be employed to charge future smart versions too.

Recharged by your tears

But that’s not the only way to charge up the lenses, as Lee says they can also be charged while in your eye, due to our tears containing glucose. That’s right, the more you cry, the more your smart contact lens battery will recharge. That’s sure to make for an interesting advertising campaign when release time comes. Don’t expect it to be powering any contact lenses soon though. At the moment, the battery is a work in progress and only lasts for a few hours on a single charge. And its power output isn’t enough to sustain a wireless connection or power any onboard storage, which would be essential for smart eyewear.

The development of a tiny, superthin battery is another step forward in the quest to create a pair of smart contact lenses. We’ve been seeing and hearing about smart contact lens technology for many years, including early versions made with lens experts Bausch + Lomb and shown during CES 2021, and versions made for medical purposes too. It’s not the first time scientists have claimed to be inspired by Mission: Impossible either, as a professor from Nanjing University cited the same movie while discussing a set of battery-free eye-tracking smart lenses this year.

While we wait for smart contact lenses, take a look at the Ray-Ban Meta smartglasses, one of the best smart eyewear products we’ve tried. You have to use a USB C cable to recharge them though.