Swiss Federal Institute of Technology researchers published a paper in Nature Communications describing an ultra-thin thin circuit that is small and flexible enough to wrap around a human hair or lay on top of a contact lens, opening up some interesting applications.
To develop the circuit, the researchers had to choose a polymer that was thin and transparent, but also tough enough to have circuitry etched into it. They also had to use a secondary polymer for support that could be dissolved in water once the circuitry was complete. They settled on parylene and a vinyl variant, respectively. Parylene, which is sometimes used as a moisture and environmental barrier for materials like rubber, plastic and electronics, is biocompatible and very stable.
Once the parylene is adhered to the vinyl and the circuitry is etched on, the vinyl is dissolved away in water and a thin sheet roughly a sixtieth the width of a human hair containing the electronic components remains. It can bend around objects as thin as a human hair without breaking.
The researchers were able to attach a film to a contact lens, creating a device that could be used to monitor, for example, the eye pressure of someone who has glaucoma. But there are lots of other potential uses, including long-term implants, solar cells or environmental sensors.
For now, the circuit is just a proof-of-concept. Convincing the body to accept a foreign object as an implant is more complicated than using a biocompatible material. Components like batteries and sensors also tend to be much larger than the tiny circuit, so a full system could take quite some time to develop.