8.10.2010 Thesis: Printable conducting polymers make electronics bend

Conducting polymers have been studied since their discovery in 1970s. They have shown potential to be used in many organic electronics applications like sensors, solar cells, displays and RFID tags. The applications of conducting polymers have the advantage of flexibility and low cost processing by printing when compared to traditional silicon-based electronics.

However, often the polymers seem to have a life of their own and it might be difficult to predict their electrical properties. VTT’s research scientist Marja Vilkman studies this challenge in her PhD thesis, titled “Structural investigations and processing of electronically and protonically conducting polymers”. Her thesis aims at taking control over the electrical properties of conducting polymers by modifying their structural order.

One example of utilisation of conducting polymers in packaging applications is the humidity memory, which is presented in the thesis. The humidity memory is based on a conducting polymer, polyaniline, which is doped to a conducting state with a moisture-sensitive counter-ion. The counter-ion (needed for reaching the high conductivity of the polymer) crystallises and phase-separates in normal humid air. This reaction leads to permanent loss in conductivity, which allows detection of past humid conditions. This kind of sensor can be attached inside a package to show that the contents have not been exposed humid conditions in any stage during storage. The information can be read even through the package electrically with non-contact capacitive measurements.

To be able to lower the fabrication costs, an important field of research in organic electronics is large-scale production. Also this aspect is studied in this thesis and novel printing methods for conducting polymers are presented. For example, the humidity memory can be easily printed with e.g. flexographic printing machines.

As an outcome, this thesis takes a step from the laboratory towards applications of conducting polymers. It shows how we can control the electrical properties of polymers by structural control and how the polymers can be processed by printing.

The thesis of Marja Vilkman was defended for the degree of Doctor of Science in Technology at The Aalto University School of Science and Technology, in a public examination and debate at Aalto University on Friday, 8 October 2010.

Link to the thesis:

http://www.vtt.fi/inf/pdf/publications/2010/P744.pdf

Additional information:

Marja Vilkman
Research scientist
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Tel. +358 20 722 7132