Transparent, flexible metal oxide film, printed at room temperature

Scientists have used a new printing process to develop a transparent conductive oxide that is crucial for applications such as cell phone screens and computer monitors.

In a new study, researchers from North Carolina State University, Pohang University of Science and Technology (POSTECH), Ulsan National Institute of Science and Technology and the University of Waterloo have jointly developed a type of room-temperature metal oxide film.

Scientists demonstrated the new technique for printing thin metal oxide films at room temperature. These films are transparent, flexible and highly conductive and can also be used at high temperatures.

This printing process uses liquid metals to deposit metal oxide layers onto surfaces, creating circuits that are both robust and versatile.

Michael Dickey, a professor of chemical and biomolecular engineering at North Carolina State University, told Interesting Engineering that the transparency of metal oxide films is critical for some applications, such as cell phone screens and computer monitors that require electrodes.

“The electrodes are used to make your mobile phone touch sensitive, and they can also be used to control the light pixels in a monitor or television. In this case, the oxide must be transparent to let light through (from the screen to your eyes),” he said.

Alluding to the importance of the new development, the scientist said IE that the thin nature of the material makes the film flexible.

“Our film is incredibly thin – only four nanometers. Therefore, it can be bent/folded without breaking,” said Dickey.

“Oxides have mechanical properties like glass… of course, a thick piece of glass (like a window in your house) would break if you were to bend it. Our glass can bend because it is thin. We believe this could open up new applications for these materials (e.g. flexible electronics). For example, we have succeeded in applying the film to a sheet.”

Surprisingly, the researchers found that the oxide was stable at high temperatures. This suggests that the metal oxide films could be used at high temperatures. But it also means that they should be very stable under ambient conditions over long periods of time.

“Essentially, it means the films are durable and could be suitable for high-temperature applications (the latter doesn’t immediately spring to mind, but you can imagine sensors or electronics operating in extreme environments),” Dickey added.

Enables the production of transparent, flexible circuits

Despite their high conductivity and metallic properties, these thin metal oxide films retain a high degree of transparency.

This makes them particularly valuable for applications where both conductivity and transparency are important, such as touchscreens and display technologies.

Conventional methods for producing metal oxides for electronics are time-consuming, expensive and require high temperatures.

However, the new process represents a more efficient approach in which metal oxide films are generated and deposited at room temperature, enabling the production of transparent, flexible circuits.

Now the team of scientists hopes to extend this printing technology to other materials. Dickey explained that liquid metal was used for printing. To print aluminum oxide, for example, you would have to melt aluminum, which requires very high temperatures.

Using the new process, the team was able to demonstrate that it is possible to print aluminum oxide at near room temperature by adding only a tiny amount of aluminum to gallium (a metal with a low melting point).

“Inspired by these results, we are interested in investigating other materials using this technique and studying the properties of the resulting films,” says the professor.

The study was published today (15 August 2024) in the journal – Science.