About two decades ago, researchers at Linköping University developed a method to print circuits using a printing press, and now, seventeen years later, they continue to make major advancements in this field. In a recently published study, researchers at Linköping University and RISE, Campus Norrköping, have demonstrated that screen printing organic electrochemical transistors is possible by successfully printing more than 100 of them on a plastic substrate no bigger than an A4 sheet of paper.
These large-scale integrated circuits, LSI, can be used, for example, to power an electrochromic display, itself manufactured as printed electronics. Image Credit: Thor Balkhed, Linköping University.
One of the biggest challenges to creating printed circuits is creating a mesh screen small enough to allow for very fine, and precise lines to be masked off. Thanks to the technology boom of the last two decades, the graphics industry has continued to push the miniaturization of printing screens, and this has allowed the team at Linköping and RISE to print lines just 100-micrometers wide. When combined with the specialized “inks” the team has worked tirelessly to develop, very precise circuits can be printed.
“The advantage we have here is that we do not need to mix different manufacturing methods: everything is done by screen printing and in relatively few processing steps. The key is ensuring that the different layers end up in exactly the right place”, says Peter Andersson Ersman, a researcher in printed electronics at the RISE research institute.
Ersman and the rest of the research team published their initial findings on screen printing electronic circuits in 2017, but there was still a lot to work out. Since that publication, the team has worked to further reduce the scale at which they can print functional circuits as well as ensuring that the printed transistors in these circuits are as close to perfect as possible. Researchers also focused on solving the problem of how to property interface their screen printed circuits with silicon-based electrical components such as ICs, displays, etc.
“One of the major advances is that we have been able to use printed circuits to create an interface with traditional silicon-based electronic components. We have developed several types of printed circuits based on organic electrochemical transistors. One of these is a shift-register, which can form an interface and deal with the contact between the silicon-based circuit and other electronic components such as sensors and displays. This means that we can now use a silicon chip with fewer contacts, which needs a smaller area and is in this way cheaper”, says Magnus Berggren, professor of organic electronics and director of the Laboratory of Organic Electronics at RISE.
Some of the researchers behind the breakthrough: Peter Andersson Ersman, RISE, Simone Fabiano, LiU, Jan Strandberg and Roman Lassnig, RISE.
With the high-quality ink’s, and ultra-fine mesh screens, researchers have been able to greatly improve the printed circuit’s quality and reliability, and as a result, have been able to fit over 100 organic electrochemical transistors onto a small polymer substrate about the size of a sheet of paper. These so-called “large-scale integrated circuits,” or LSI for short, can be used to power other printed electronics such as electrochromic displays, or even as a way to integrate tracking sensors directly into a product’s packaging for logistics and end-user information purposes.
“We can now place more than 1000 organic electrochemical transistors on an A4-sized plastic substrate, and can connect them in different ways to create different types of printed integrated circuits”, says Simone Fabiano, head of research in organic nanoelectronics in the Laboratory of Organic Electronics.
“This is a decisive step for a technology that was born at Linköping University just over 17 years ago. The result shows that we are again leading the field, thanks to the close collaboration between basic research at the Laboratory of Organic Electronics, LOE, and applied research at RISE”, says Magnus Berggren.
Source: https://liu.se/en/news-item/integrerade-kretsar-produceras-i-tryckpress
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