Researchers have developed an innovative method to print thin metal oxide films at room temperature, paving the way for transparent, flexible circuits that are both durable and capable of functioning at high temperatures.
This breakthrough, detailed in a paper published in Science, represents a significant advancement in the creation of electronic materials.
Traditionally, producing metal oxides for electronics has required specialized equipment that operates at high temperatures, making the process slow and expensive.
Michael Dickey, a professor at North Carolina State University and co-author of the study, explained, “We wanted to develop a technique to create and deposit metal oxide thin films at room temperature, essentially printing metal oxide circuits.”
Metal oxides are crucial in electronics, with some being both conductive and transparent—essential for devices like touch screens on smartphones and computer monitors.
However, making these films at room temperature has been challenging until now.
The researchers developed a novel technique that uses a meniscus of liquid metal to create the metal oxide films.
A meniscus is the curved surface of a liquid that forms at the edge of a container. In this case, when liquid metal meets air, it forms a thin metal oxide skin on its surface.
To create the thin films, the researchers placed liquid metal between two glass slides, allowing a small meniscus of liquid metal to extend beyond the slides’ ends.
As they moved the meniscus across a surface, the metal oxide from the meniscus adhered to the surface, leaving behind a solid, incredibly thin film—about 4 nanometers thick.
Despite being deposited as a liquid, the metal oxide film on the surface is solid, making it suitable for printing circuits.
The team successfully tested the technique with various liquid metals and metal alloys, finding that each metal altered the composition of the oxide film. They could also create stacked layers of thin films by making multiple passes with the “printer.”
One surprising discovery was that the printed films are transparent but have metallic properties, making them highly conductive.
Adding a small amount of gold to the films helped prevent the conductive properties from degrading over time, as the gold bonds with the oxide in a unique way.
The films were also found to retain their conductive properties at high temperatures. A film 4 nanometers thick maintained its conductivity up to nearly 600 degrees Celsius, while a 12-nanometer film remained conductive at temperatures up to 800 degrees Celsius.
The researchers demonstrated the technique’s versatility by printing metal oxides onto a polymer, creating flexible circuits that remained functional even after being folded 40,000 times. The films can also be transferred to unconventional surfaces, such as leaves, opening up possibilities for electronics in new and creative places.
Dickey mentioned that the team is preserving the intellectual property for this technique and is interested in collaborating with industry partners to explore potential applications, marking an exciting step forward in flexible and robust electronic materials.
