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KIT researchers work towards compostable printed electronics

06 September 2015

Young researchers at Karlsruhe Institute for Technology (KIT) are developing printed electronics made of compostable natural materials using sustainable processes.

Organic light-emitting diodes (OLEDs) can be produced easily and at low cost. Thanks to compostable materials, they are also made sustainable (photo: KIT)

Semiconductors and dyes made of plant extracts, or insulators made of gelatin may not be as long-lived as their inorganic alternatives, but they easily survive the service life of disposable electronics, says Dr Gerardo Hernandez-Sosa, leader of the Biolicht Young Investigator Group at KIT. After use, electronic devices made with these materials can simply be thrown away into the biowaste bin or on compost heaps, where they will simply rot away.

So far, this has not been the case for conventional printed electronics, such as organic light-emitting diodes (OLEDs). “We call all synthetic materials that are based on carbon 'organic' but this term does not tell us anything about environmental compatibility,” says Dr Hernandez-Sosa. 

The carrier foil of OLEDs – the paper equivalent for electronic inks – is made of the same plastic material as conventional beverage bottles. The Biolicht group only uses easily biodegradable materials that can be found in nature - starch, cellulose, or chitin are suitable for the carrier foils, for instance.

For the inks, the young scientists are currently trying to identify environmentally compatible materials with the desired electrical properties; hard gelatin that is used for making drug capsules is suitable for insulation, for example.

Selecting a suitable solvent is also underway. It has to be in liquid form at temperatures used for printing. Contrary to conventional ink, it must not penetrate into the carrier material, but should form a closed liquid film on the carrier without dripping off. A solvent that is too thick plugs the pores of the printer, while a solvent too thin disperses on the carrier foil and does not cover it homogeneously.

The properties of the dry material film, however, are crucial to the function of these compostable electronic components: its thickness (less than a thousandth of a millimetre) must not vary by more than 5 percent.

Despite these obstacles, the KIT group is confident that compostable organic electronics will be ready for the market within three years.

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