Previously, use has been made of nano-canals and nano-pores to actively control the concentration and transport of ions but those components are difficult to produce and function poorly when the salt content is high, obviously something that would be an issue in interaction with biological systems.
"To get around these problems, we exploited the similarity between ion-selective membranes - plastics that only conduct ions of one charge - and doped semiconductors, such as silicon. It was previously known that it is possible to produce diodes from such membranes. We took it a step further by joining two ion diodes into a transistor," says Klas Tybrandt, a doctoral candidate in organic electronics at Linköping University and a member of the research center OBOE (organic bioelectronics), a group funded by the Sweden's Foundation for Strategic Research..
When an ion transistor is connected to cultivated nerve cells, it could be used to control the supply of the signal substance acetylcholin locally to the cells. The successful result demonstrates both that the component functions together with biological systems and that even tiny charged biomolecules can be transported without difficulty.
"Since the ion transistor is made of plastic, it can be integrated with other components we are developing. This means we can make use of inexpensive printing processes on flexible materials. We believe ion transistors will play a major role in various applications, such as the controlled delivery of drugs, lab-on-a-chip and sensors," says Magnus Berggren, Önnesjö professor of organic electronics at Linköping.
Citation: Klas Tybrandt, Karin C. Larsson, Agneta Richter-Dahlfors, and Magnus Berggren, 'Ion bipolar junction transistors', PNAS. Published online before print May 17, 2010, doi: 10.1073/pnas.0913911107