In fantasy movies about the distant future, we can often see lens technology superimposing virtual elements on top of the real world: environmental data, messages from people, business tips, and other information. Mankind has been trying to make this a reality for many years, but so far it has not achieved significant success – to some extent precisely because of the problem of charging such contact lenses. For all the tasks described today, we use fairly large headsets, but in the near future everything may change.

a new hope

We already use prototypes of dream technology for vision correction, health monitoring, and even diagnosing and treating chronic diseases such as diabetes and glaucoma. In the future, lenses will be able to record and transfer everything their wearer sees and hears to cloud storage.

However, in order to realize this potential, a safe and suitable battery needs to be created. Existing batteries based on wire or induction coil contain metal and are not suitable for visual use due to health risks..

• Developed at NTU, the battery is made of biocompatible materials and does not contain wires or toxic heavy metals like lithium-ion batteries.
• The glucose-based coating reacts with sodium and chloride ions in the saline solution in which the lenses are usually placed for overnight storage.
• The water in the battery acts as an electrical conductor and ensures the transmission of the electrical current formed as a result of the described chemical reaction.

Testing the battery using a solution that mimics the composition of human tears showed that its operating capacity increases by an additional hour after every twelve hours of continuous operation with this charging method. It is also possible to charge the battery in the traditional way from an external source.

This breakthrough in battery technology could be a pivotal moment in the development of smart contact lenses and other medical devices. The safety, flexibility, and ability to charge from saline or even tears make this battery an ideal candidate for integration into future medical devices.