The march of science can be both interesting and scary at the same time. The variety of smaller and smaller electronics and electronic sensors boggles the mind. New ultra-thin flexible transparent electronics can wrap around a hair.
**Giovanni A. Salvatore, Niko Münzenrieder, Thomas Kinkeldei, Luisa Petti, Christoph Zysset, Ivo Strebel, Lars Büthe, Gerhard Tröster. Wafer-scale design of lightweight and transparent electronics that wraps around hairs.Nature Communications, 2014; 5 DOI: 10.1038/ncomms3982
In Professor Gerhard Tröster’s Electronics Lab, scientists have been researching flexible electronic components, such as transistors and sensors, for some time now. The aim is to weave these types of components into textiles or apply them to the skin in order to make objects ‘smart’, or develop unobtrusive, comfortable sensors that can monitor various functions of the body.
Within a year, Münzenrieder, together with Giovanni Salvatore, has developed a procedure to fabricate these thin-film components. The membrane consists of the polymer parylene, which the researchers evaporate layer by layer into a conventional two-inch wafer. The parylene film has a maximum thickness of 0.001 mm, making it 50 times thinner than a human hair. In subsequent steps, they used standardised methods to build transistors and sensors from semiconductor materials, such as indium gallium zinc oxide, and conductors, such as gold. The researchers then released the parylene film with its attached electronic components from the wafer.
An electronic component fabricated in this way is extremely flexible, adaptable and — depending on the material used for the transistors — transparent. The researchers confirmed the theoretically determined bending radius of 50 micrometers during experiments in which they placed the electronic membrane on human hair and found that the membrane wrapped itself around the hair with perfect conformability. The transistors, which are less flexible than the substrate due to the ceramic materials used in their construction, still worked perfectly despite the strong bend.
Smart contact lens measures intraocular pressure
Münzenrieder and Salvatore see ‘smart’ contact lenses as a potential area of application for their flexible electronics. In the initial tests, the researchers attached the thin-film transistors, along with strain gauges, to standard contact lenses. They placed these on an artificial eye and were able to examine whether the membrane, and particularly the electronics, could withstand the bending radius of the eye and continue to function. The tests showed, in fact, that this type of smart contact lens could be used to measure intraocular pressure, a key risk factor in the development of glaucoma.