Making Flexible and Thin-Film Electronics More Durable
Researchers from Daegu Gyeongbuk Institute of Science and Technology (DGIST) in South Korea have reportedly developed an approach for controlling the random formation of cracks in flexible thin-film conductors.
This approach is said to greatly increase the durability of flexible electrodes and transistors by mitigating the damage that takes place when they bend and fold. If commercialized, the team’s approach could help make realer the prospect of widespread flexible electronics, technology which has many promising applications—from solar cells to health sensors—and has prompted researchers the world over to develop novel ways to enhance their performance and durability.
The team’s research paper describes the approach and was published in ACS Applied Materials & Interfaces on April 22.
Peppering Conducting Film with Holes
The approach is very simple: Take a standard flexible conducting film and fill it with micrometer-sized holes in a zig-zag pattern. Inspiration for this approach was drawn from civil engineering as Professor Jae Eun Jang, the research team’s leader, explains: “We happened to be passing by a construction site, when we saw steel plates with holes, often used in construction. We knew that these steel plates with holes are used to reduce stress. We thought that this method could also be a solution in the micrometer world and, based on this idea, we began conducting experiments.”
Professor Jae Eun Jang (rear) and Ms Su Jin Heo (front) next to their experimental setup which enabled them to observe how cracks form in thin flexible conductors. Image credit: DGIST.
In civil engineering, the word “stress” is used to refer to the forces that the particles of a material exert on one another. External forces increase the stress imposed on a material and can induce cracking. In thin-film flexible conductors, these cracks form in random locations when they are bent. In contrast, the DGIST team’s approach enables them to control where cracks form because the micrometer-sized holes alter the stress distribution so that cracks only form at specific points and propagate a short distance.
Enduring Thousands of Bending Motions
The team put their thin-film flexible conductor through its paces with a series of simulations and experiments. They observed that it could endure thousands of bending motions. “Our devices were able to maintain conductivity up to 300,000 bending cycles, which means that they can be bent over 80 times a day for 10 years”, Jang said.
Not only is the DGIST thin-film flexible conductor more durable but it is inexpensive and easy to adopt using equipment already deployed across the display industry, too. The team believes that the material could be used to enhance the reliability of various electrical devices in flexible and wearable applications.