Researchers have for the first time printed complete integrated circuits that have more than 100 organic transistors, a breakthrough in the quest to use printing to create complex next-generation electronic and computing devices.

Some of the researchers behind the breakthrough to developed complete, integrated circuits using a novel screen-printing process: Peter Andersson Ersman, Research Institute of Sweden, or RISE; Simone Fabiano, Linköping University; and Jan Strandberg and Roman Lassnig, RISE. (Image source: Thor Balkhed)

A team of engineers at two Swedish institutions–Linköping University and RISE (Research Institutes of Sweden), Campus Norrköping—achieved the milestone using only screen printing rather than the multiple manufacturing methods to create integrated circuits. “Everything is done by screen printing, and in relatively few processing steps,” he said in the statement. “The key is ensuring that the different layers end up in exactly the right place,” said Peter Andersson Ersman, a researcher in printed electronics at RISE.

The team used this process to place more than 1000 organic electrochemical transistors on an A4-sized plastic substrate, and connected them in different ways to create various types of printed integrated circuits. The work is the culmination of 17 years of research, including an advancement in 2017 to use screen printing to fabricate circuits that set the stage for the latest achievement.

Tweaking the process

In the past two years, the team has made a number of changes to the process and the result includes a reduction in circuit size; spacing the transistors in the circuit more closely to increase the quality of the product; and achieving the integration of silicon-based circuits that can process signals and communicate with the surroundings.

“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,” Magnus Berggren, professor of organic electronics at Linköping University, explained. “We have developed several types of printed circuits based on organic electrochemical transistors.” 

One of these circuits is what’s called 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 advancement means researchers can use a silicon chip with fewer contacts, which requires a smaller area and thus is less expensive.

Ink also was a major factor in printing a complete integrated circuit with such a large amount of transistors. The team used the polymer PEDOT:PSS as their material for printing the circuits; it’s one that is widely used in the world in the field of organic electronics.

The material allowed for the development of ink that could be used with the screen-printing frames—which has meshes that can print extremely fine lines–to create smaller components but without losing product quality.

The team published a paper on its work in the journal Nature Communications.

The large-scale integrated circuits that researchers printed have myriad uses for electronics being developed for the Internet of Things (IoT). For example, they can be used to create an electrochromic display, which also can be manufactured using a printing process.

Elizabeth Montalbano is a freelance writer who has written about technology and culture for more than 20 years. She has lived and worked as a professional journalist in Phoenix, San Francisco and New York City. In her free time she enjoys surfing, traveling, music, yoga and cooking. She currently resides in a village on the southwest coast of Portugal.