The technique developed at the Swiss Federal Institute of Technology (ETH; Zurich) involves building a membrane made of parylene, which is evaporated layer by layer until a conventional 2-in. wafer is formed. Standard methods are used to incorporate transistors, sensors, and conductors. The parylene film with the attached electronics is then released from the wafer.
In addition to being flexible—in lab tests, the film and electronics exhibited a 50-micrometer bending radius—the finished device could be transparent, depending on the material used for the transistors.
So-called smart contact lenses that could continuously measure intraocular pressure, a key indicator of glaucoma development, are one possible application, according to researchers Niko Münzenrieder and Professor Gerhard Tröster. They also cite wearable biosensors and flexible solar cells as areas of interest.
In lab tests, Münzenrieder and Tröster attached the thin-film transistors and strain gauges to contact lenses fitted onto an artificial eye. The tests showed that the membrane and electronics could withstand the bending radius of the eye and continue to function.
A number of other technical challenges remain, however, before the technology can leave the lab. Topping the to-do list are a suitable method for attaching the electronic component to the contact lens and determining an energy source.