Researchers have created a flexible battery as thin as a human cornea that stores electricity when immersed in saline solution and could one-day power smart contact lenses.
“Smart contact lenses to be powered by a ground-breaking battery fuelled by tears.”
Smart contact lenses are high-tech contact lenses that can display visible information on our corneas as well as access augmented reality. Current applications include assisting in vision correction, monitoring wearers’ health, and identifying and treating diseases in people with chronic health conditions such as diabetes and glaucoma. Smart contact lenses could be developed in the future to record and transmit everything a wearer sees and hears to cloud-based data storage.
A new tear-powered battery will power smart contact lenses
Human tears, which contain sodium and potassium ions in lower concentrations, could also be used to power the battery. The researchers demonstrated that by testing the current battery with a simulated tear solution, the battery’s life would be extended by an hour for every twelve-hour wearing cycle. An external power supply can also be used to charge the battery conventionally.
“Earlier methods for lens battery operation had shortcomings as one side of the battery electrode would be charged while the other remained unchanged. Through a novel combination of enzymatic and self-reduction reactions, we can charge both electrodes of a battery. Aside from the charging mechanism, it generates electricity using only glucose and water, both of which are safe for humans and would be less harmful to the environment when disposed of than conventional batteries.”
“The commonly used charging mechanism for smart contact lens batteries usually involves integrating metal electrodes into the lens, potentially posing a hazard if exposed to the naked human eye. Meanwhile, induction charging, which is similar to a wireless charging pad for a smartphone, requires a coil to be in the lens to transmit power. Our tear-based battery eliminates the two potential issues that these two methods present, while also making room for future innovation in the development of smart contact lenses.”
Smart contact lenses are high-tech contact lenses that can display visible information on the corneas and allow access to augmented reality. Current applications include assisting in vision correction, monitoring wearers’ health, and identifying and treating diseases in people with chronic health conditions such as diabetes and glaucoma. Smart contact lenses could also be created to record and transmit everything a wearer sees and hears to a cloud-based data storage system.
Smart contact lenses represent the marriage of cutting-edge technology and healthcare. These are not ordinary contact lenses; they contain micro-technologies that can project visual data directly onto our corneas, acting as miniaturized computer screens for our eyes.
Description of the smart lenses
The battery, which is about 0.5mm thick, generates electrical power by reacting with the basal tears – the constant tears that form a thin film over our eyeballs – to power the devices embedded within the lenses.
When the glucose oxidase coating in the contact lenses reacts with the sodium and chloride ions in the tears, the flexible and flat battery discharges electricity through a process known as reduction, generating power and current within the contact lenses. The team demonstrated that the battery could generate a current of 45 microamperes and a maximum power of 201 microwatts, enough to power a smart contact lens.
According to laboratory tests, the battery can be charged and discharged up to 200 times. The team recommends that the battery be charged while the user is sleeping for at least eight hours in a suitable solution containing a high concentration of glucose, sodium, and potassium ions.
Smart Lenses: Vision Correction Meets Health Tech and Augmented Reality
These lenses were created to address common eye conditions, providing a modern solution for vision correction. Aside from vision correction, these smart lenses are now equipped with sensors and data transmission mechanisms that can continuously monitor the wearer’s health metrics.
The lenses can monitor intraocular pressure in glaucoma patients, providing real-time data that can be critical for managing the condition. They can warn wearers about potential health issues, provide medication reminders, and even provide augmented overlays to help with daily activities.
Saline-powered, cordless safe battery
The battery is made of biocompatible materials and lacks wires and toxic heavy metals found in lithium-ion batteries or wireless charging systems. It has a glucose-based coating that reacts with the sodium and chloride ions in the surrounding saline solution. Simultaneously, the water in the battery acts as the “wire” or “circuitry” for generating electricity. Existing rechargeable batteries rely on metal wires or induction coils, which are unsuitable for use in the human eye.
Intelligent Contact Lenses
These lenses feature miniature displays that may redefine our experience with augmented reality (AR), eliminating the need for bulky glasses.
Notably, the battery can also be charged by molecules found in human tears, though this isn’t enough to eliminate the need for periodic soaking in saline solution. According to tests with simulated eye tears, every 12 hours of wear results in an hour of charge from natural eye moisture.
During testing, the flexible battery produced a peak power output of 201 microwatts, which the researchers deemed sufficient to transmit data from smart contact lenses for a continuous 12-hour period. Furthermore, it also demonstrated durability with 200 charging cycles.
So far, the researchers have only demonstrated a battery — they haven’t demonstrated how it could be integrated into smart contact lenses capable of doing any of the futuristic things we want them to do.
The next steps will be to increase the amount of current that the flexible battery can discharge and to collaborate with several companies to incorporate the technology into smart contact lenses.