Printing Electronic Parts for Next-Generation Technologies
Custom inks and new printing techniques allow creating strong transistors for smart devices
Tiny electronic parts, known as microelectronics, may one day be printed like words on a page, thanks to recent research from scientists at the U.S. Department of Energy’s (DoE) Argonne National Laboratory. Building on past progress in printed electronics, the team found a way to make strong, low-power electronic switches, called transistors, by mixing special inks with a special printing method.
These switches control the flow of electrical current to turn circuits on and off, use very little power, are built to last, and show new behaviors not seen in earlier printed devices. This research could lead to flexible sensors, smart windows, and other new technologies that need reliable and energy-saving electronics.
The scientists used a method called aerosol jet printing, which is similar to an inkjet printer. But instead of regular ink, it uses specially made ink made from tiny nanoparticles. The printer turns the ink into a fine mist and sprays it onto a surface, building up layers to form electronic parts.
Unlike regular manufacturing, which often needs expensive equipment and high temperatures, aerosol jet printing works at lower temperatures and can print on flexible or even 3D surfaces. This method makes it easier and faster to make and test new electronic designs.
To fine-tune these inks, the team used the Center for Nanoscale Materials (CNM) at Argonne to observe how nanoparticles stick together, how they change with heat, and check the stability and makeup of the dried films. These insights helped improve the ink formulas. They also used the 2-ID-E hard X-ray microprobe at Argonne’s Advanced Photon Source (APS) to see the shape and make-up of the printed devices, along with high-resolution X-ray spectroscopy studies at Brookhavens National Synchrotron Light Source II (NSLS-II). CNM, APS, and NSLS-II are all part of the DOE Office of Science user facilities.
A key ingredient in these printed devices is vanadium dioxide. This material is special because it can act like a wire, allowing electricity to flow, or like an insulator, blocking electricity. This ability to switch back and forth is important for making electronic circuits and memory devices, which store and process information.
To control the flow of electricity in the transistors, the team used a process called redox gating. In simple terms, this means they used a chemical reaction to add or remove electrons from the vanadium dioxide. By applying a small voltage, less than what a typical battery uses, they could turn the transistor on or off. This method is less harmful than other techniques, which could damage the material and cause devices to wear out quickly.
In lab tests, the printed transistors operated at voltages as low as 0.4 to 0.5 volts and lasted for more than 6,000 on-off cycles, which is much longer than earlier printed devices. The switches also responded quickly, changing states in about one second.
We chose printing methods for two main reasons, said Argonne Materials Scientist Yuepeng Zhang. First, printing allows for fast prototyping and quick design improvements, which helps us optimize materials and device structures quickly. Second, printed electronics offer benefits for device function, especially because our devices show strong and controlled current responses to voltage, making them suitable for printed logic devices and special applications.
When the printed transistor was turned on using a small control signal of 0.5 volts, it allowed about 50% more electricity to flow through it compared to when it was off. In other words, the device could increase the flow of electric current by half with just a small amount of power. This shows that the transistor can control electricity reliably using very little energy, which is important for making low-power and flexible electronic devices.
Wei Chen, a chemist from Argonne and the University of Chicago, stressed the durability of the new devices. Redox gating is strong and does not damage the materials, so we can run thousands of cycles without any problems, he said. In earlier methods, devices could only run a few times sometimes just 10 cycles before failing. Our devices can run thousands of cycles without issues.
Right now, these printed transistors are bigger and slower than the tiny silicon chips used in most electronics. But this research shows that it is possible to make strong, low-power devices using printing techniques.
Chen added, From my perspective, the next step is logic devices. We have been in touch with industry partners interested in testing our devices for logic applications, which are the basic building blocks for computers. That is something I would like to pursue.
They are also exploring how these printed devices could be used in neuromorphic computing, an area that imitates the way the human brain processes information.
To move printed electronics from the lab to real products, the researchers say more teamwork is needed between scientists and industry. They also believe that artificial intelligence and machine learning could help improve the printing process and make development faster.
Printing involves many variables to adjust, and machine learning can help us find the best settings more quickly, Zhang said.
With more research and collaboration, printed hybrid electronics could help make future technology more flexible, affordable, and energy efficient.
The results of this research were published in Advanced Materials Technology.
Source: Brookhaven National Laboratory
