Biodegradable Integrated circuits - Transient Electronics
A relatively new type of microcircuit is also fully biodegradable. Intended for implantation into the body, it is a class of circuitry which, if its protective shell is ruptured; dissolves quickly and completely in the body's fluids.
Researchers at the University of Illinois, in collaboration with Tufts University and Northwestern University created the class of electronic circuit, which they have dubbed transient electronics.
It's not just suitable for implants either. Transient electronics get their name, because they dissolve completely in water or any fluid solution that involves water. As such they are ideal for the electronic components of interactive newspapers, magazines or fliers. Protected from the elements by a thin plastic coating which also serves as the display screen they break down completely when that coating is torn open ready for recycling.
John A. Rogers, the Lee J. Flory-Founder Professor of Engineering at the U. of I., who led the multidisciplinary research team stated: From the earliest days of the electronics industry, a key design goal has been to build devices that last forever with completely stable performance. But if you think about the opposite possibility devices that are engineered to physically disappear in a controlled and programmed manner then other, completely different kinds of application opportunities open up.
He also discussed a third application for such electronics: sensors for a sensor web that you actually wish to fade and disappear over time. One such example was a scattering of chemical sensors cast by the handful into a contaminated site. Over time the wind and the rain will break the chemicals down, but the sensors would normally remain. Embed the electronics in a slow-breakdown biodegradable casing however, and as the wind and rain remove the chemical spill, the sensors themselves follow soon after.
Transient electronic systems harness and extend various techniques that the Rogers group has developed over the years for making tiny, yet high performance electronic systems out of ultrathin sheets of silicon. In transient applications, the sheets are so thin that they completely dissolve in a few days when immersed in biofluids. Together with soluble conductors and dielectrics, based on magnesium and magnesium oxide, these materials provide a complete palette for a wide range of electronic components. So far they have fabricated transient transistors, diodes, wireless power coils, temperature and strain sensors, photodetectors, solar cells, radio oscillators and antennas, and even simple digital cameras.
Every single one of these items contains electronics which rapidly break down when exposed to water. They break down completely with barely a trace remaining and the materials they break down into are entirely non-toxic so they are ideal for implantation within the body.
Currently the biodegradable case for the electronics, is a deceptively simple cocoon of silk. This gives a great deal of flexibility, as the silk slowly dissolves at a rate determined by its structure. Anywhere from a dissolution in minutes, to a dissolution spanning years, is possible with current reproducible silk structures. Only when the silk itself dissolves, do the electronics themselves, previously safe within the silk, begin to degrade.
The different applications that we are considering require different operating time frames, Rogers said. A medical implant that is designed to deal with potential infections from surgical site incisions is only needed for a couple of weeks. But for a consumer electronic device, youd want it to stick around at least for a year or two. The ability to use materials science to engineer those time frames becomes a critical aspect in design.
Its a new concept, so there are lots of opportunities, many of which we probably have not even identified yet Rogers said. Were very excited. These findings open up entirely new areas of application, and associated directions for research in electronics.