In the world of smart contact lenses, one of the biggest challenges is finding a safe and efficient way to power these innovative devices. However, scientists from Nanyang Technological University (Singapore) may have found a solution to this problem by using an ultra-thin battery charged by tear fluid.
Smart contact lenses are being developed for a variety of purposes, including monitoring glaucoma, delivering eye medication, and even projecting augmented reality images. However, traditional methods of powering such lenses have proven to be less than ideal. Most commonly, metal electrodes are used, which can be harmful to the naked eye. Alternatively, induction charging is used, requiring a metal coil in the lens, similar to wireless charging pads for smartphones.
A Singapore research team led by Associate Professor Lee Sok Woo has proposed an alternative solution – a 0.5mm thick battery integrated into the lens that uses water and a coating of an enzyme called glucose oxidase. When the battery is immersed in the basal tear fluid that naturally coats our eyes, the enzyme reacts with the sodium and chloride ions in the fluid, creating an electrical charge in the water that makes up the battery.
In laboratory tests conducted on a human eye simulator, a battery charged with tear fluid produced a current of 45 microamps and a maximum power of 201 microwatts. According to the researchers, this is enough to wirelessly transmit data from the smart contact lens for at least 12 hours. Currently, the battery can withstand up to 200 charge/discharge cycles, while lithium-ion batteries are typically designed for 300-500 cycles.
To ensure optimal performance, the researchers recommend placing the lens overnight in saline solution for at least eight hours to fully charge it for the day.
This groundbreaking research was published in the journal Nano Energy and has attracted the attention of experts in the field. Dr. Yoon Jeonghoon, one of the original authors of the study, explains the significance of this development, “The most common battery charging system for smart contact lenses requires metal electrodes in the lens, which are harmful when exposed to the naked human eye. In contrast, another method of powering lenses – induction charging – requires a [metal] coil in the lens to transfer energy, similar to a wireless charging pad for a smartphone.”
A battery charged by tear fluid opens up new possibilities for the future of smart contact lenses. With a safe and discreet power source, these lenses will be able to further develop their capabilities and applications. The potential impact on healthcare and augmented reality is huge, as these lenses could revolutionize the monitoring and treatment of eye diseases and improve our visual experience.