is researching the potential for printing complete electronic circuits, including transistors, resistors and capacitors, with separate backing from both the DTI and the MOD.
In the consumer sector the technology being investigated could help reduce the cost of many electronic products. In the defence field it could enable electronic functionality to be added to structural components of systems or to personal and protective clothing economically, with minimal increase in mechanical complexity and with negligible weight growth.
The DTI is providing funding of around £200,000 for an initial two-year research programme to develop materials and processes and then look at applying the technology to large displays such as flat-screen TVs and advertising boards. The MOD, through its Electronics Systems’ research budget, is providing over £750,000 for a parallel funded three-year project to investigate emerging technologies for printing electronic circuits and their consequences for defence equipment.
QinetiQ says it has already shown that a soft lithography process can be used for printing the fine metal patterns needed for thin film transistors with micron detail. This process involves creating high precision ‘stamps’ from specialised polymers which are able to deposit carefully engineered inks with very high resolution. The ink then binds metal selectively onto the surface to form the complex structures needed by active semiconductor components. Connection between the active components is then achieved by using inks loaded with conductive material that are laid down using digital printing devices like commercial ink-jet printers or plotters.
These research projects are based on using thin polymers, not silicon, as a semiconductor, adding the benefits of flexibility and improved robustness to the resulting circuits. The delivery of performance gains are not the real objective of these research programmes, rather reductions in both the cost of manufacture and the time needed to complete the design, prototyping and production cycle. New design concepts should also be possible as the electronics could be positioned within a device in previously inaccessible areas.
“Today’s large flat screen displays have a silicon switch at every pixel in order to provide a high quality image, and it is a hugely expensive process to get them all working,” explained Dr Ian Sage, the project leader at QinetiQ. “Printing the necessary electronics on the surface of the panel should be a much quicker and cheaper process which we hope will lead to larger, better and more affordable displays.”
“A lot more work is needed, but the technology also offers a huge opportunity to add electronics into defence equipment quickly and at low cost. And we can expect to see products using printed electronics beginning to appear in the high street by the end of the decade,” added Dr Sage.
A complete printed thin film transistor structure