Scientists develop ultra-thin battery that could be charged by tears

Spy movies like Mission Impossible and its sequels have introduced us to some of the unimaginable thrills and wildest innovations we can only ponder about. Well apparently, the movie inspired a team of Singapore-based Scientists to invent an ultra-thin battery for smart contact lenses. In the fourth movie of the beloved franchise, we saw agents wearing smart lenses capable of facial recognition and tracking various subjects. Inspired by this concept, Lee Seok Woo, the team’s chief scientist and associate professor at Nanyang Technological University’s School of Electrical and Electronical Engineering, set out to make it a reality.  His extensive background in battery components is what spurred him to venture into developing this wearable technology. He realized that smart contact lenses are inevitable and they will need a safe and compact battery to advance and function properly.

Contact lenses are incredibly thin at 0.5 mm, so it’s crucial to ensure that the batteries are small and flexible to avoid discomfort for the user. To address this, the team designed the battery to be only 0.2 mm thick, just twice the thickness of a human hair. Additionally, they developed a groundbreaking method to charge the battery using biocompatible saline solution, eliminating the risk of flammable materials found in lithium-ion batteries. The battery can be charged using both the conventional plug-and-charge method and a chemical method. For the chemical method, the battery simply needs to be submerged in saline solution. The lenses are implanted with electrodes, and the battery is coated in glucose. This glucose coating reacts with sodium and chloride ions to charge the battery.

After 8 hours of chemical charging, the battery will most likely be charged to 80%. Then it could be made use of for a few hours each day. There is an also an unorthodox method for charging the battery. Lee claims that since tear solution consists of glucose, the battery can be charged while the wearer is using the lens. As crazy as it sounds, the more the wearer cries, the more charge the lens has. Interestingly, the chemical approach can only charge the battery 15 times, whereas the usual way can charge it up to 200 times. 

The battery can generate an average of between 0.3 and 0.7 V using the two techniques. An AA battery operates at 1.5 V by default. The voltage is currently too low to store data or establish connectivity to the internet. However, this does not imply that such integrations are not feasible. Lee noted that the company is focusing on upgrading the smart lens’ battery. Regarding its uses, Lee has stated that those with diabetes can benefit greatly from the lens. Glucose serves as the lens’s biofuel. Lee and his group are also researching how diabetics can monitor their blood sugar levels while wearing the lens. 

The lens has a lot more possibilities, but Lee says that given the battery’s capacity, the price of the battery should be modest. After the lens is available for purchase, the battery will only run customers a few bucks.