Wednesday, January 29, 2014

Wafer-scale design of lightweight and transparent electronics that wraps around hairs

ETH Zürich contributors: Giovanni A. Salvatore, Niko Münzenrieder, Thomas Kinkeldei, Luisa Petti, Christoph Zysset, Ivo Strebel, Lars Büthe & Gerhard Tröster
A new way of making ultra thin, flexible and transparent electronics has been unveiled by researchers in Switzerland. The technique involves fabricating micron-thick electronic devices on a conventional silicon wafer, which is later detached by soaking it in water. The free-floating devices can then be placed onto a variety of biological tissues, including human skin and even a single hair. The technology could be used to make "smart" contact lenses for monitoring the pressure in an eyeball or for creating flexible solar cells.

Electronics on very thin substrates have shown remarkable bendability, conformability and lightness, which are important attributes for biological tissues sensing, wearable or implantable devices. Here we propose a wafer-scale process scheme to realize ultra flexible, lightweight and transparent electronics on top of a 1-μm thick parylene film that is released from the carrier substrate after the dissolution in water of a polyvinyl– alcohol layer. The thin substrate ensures extreme flexibility, which is demonstrated by transistors that continue to work when wrapped around human hairs. In parallel, the use of amorphous oxide semiconductor and high-K dielectric enables the realization of analogue amplifiers operating at 12 V and above 1 MHz. Electronics can be transferred on any object, surface and on biological tissues like human skin and plant leaves.

We foresee a potential application as smart contact lenses, covered with light, transparent and flexible devices, which could serve to monitor intraocular pressure for glaucoma disease.

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