The patent

Silicon transistors on plastic film

OCT-11-033: Fast and inexpensive roll-to-roll manufacturing of silicon transistors on plastic films
Inventor:  Dr Ryoichi Ishihara

Silicon transistors printed onto plastic or paper are paving the way for tablets and paper e-readers that you can fold up and put in your pocket. In 1996 Dr Ryoichi Ishihara came to Delft from the Tokyo Institute of Technology to set up a new research project focusing on thin transistors. The result was a thin layer of electronics and semiconductors on a glass surface. We use these every day in our tablets and smartphones. ‘That research has now been commercialised,’ said Ishihara.
Building on this work, in 2008 he shifted his attention to silicon transistors printed on a plastic surface. The benefits of this would be enormous – after all, plastic can be folded and rolled. This means a tablet with a foldable display and a fast and reliable electronics circuit could fit into your trouser pocket. In addition, the materials are less expensive and the production process would no longer involve huge machinery.

The transistors are printed onto a plastic surface using the technique invented by Ishihara. This can also be done on a much smaller scale – eventually even at home. That would make it possible to design your own displays. But the big surprise, according to Ishihara, is that the printing technique can also be used on paper. ‘You could print a display a print on a milk carton with  information about the milk. Or you could make a paper e-reader that you could also write on.’

What sounds even more like science fiction is Ishihara’s idea for transistors on paper for medical applications. ‘Paper and silicon are not harmful to the human body. You could swallow the electronic paper in order to take measurements inside the body.’ This is not science fiction, says the researcher, but it really could be possible using this technology.

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