Scientists Develop Solution for Transparent Electronic Devices

Scientists at the Max Planck Institute for Polymer Research (MPI-P) led by Dr. Kamal Asadi have solved a four-decade long challenge of producing very thin nylon films that can be used for instances in electronic memory components. Thin nylon films are several hundred times thinner than human hair and could thus be attractive for applications in bendable electronic devices or for electronics in clothing.

As the microelectronic industry is now shifting towards wearable electronic gadgets and electronic (e-) textiles, the involving electronic materials such as ferroelectrics should be integrated with our clothes. Nylons, a family of synthetic polymers, were first introduced in the 1920s for women's stocking and are nowadays among the most widely used synthetic fibers in textiles. They consist of a long chain of repeated molecular units, i.e.polymers, where each repeat unit contains a specific arrangement of hydrogen, oxygen, and nitrogen with carbon atoms.

In addition to using textiles, it was discovered that some nylons also exhibit so-called “ferroelectric properties”. This means that positive and negative electric charges can be separated and this state can be maintained. Ferroelectric materials are used in sensors, actuators, memories and energy harvesting devices. The advantage of using polymers is that they can be liquified using adequate solvents and therefore processed from a solution of low cost to flexible flexible films that are suitable for electronic devices such as capacitors, transistors and diodes. This makes ferroelectric polymers a viable choice for integration with e-textiles. Although nylon polymers have found significant commercial applications in fabrics and fibers over the years, their application in electronic devices has been hindered because it was impossible to create high-quality thin films of ferroelectric nylons by solution processing.

Scientists at MPI-P, in collaboration with researchers from the Johannes Gutenberg University of Mainz, and the Lodz University of Technology have now solved this forty-year-old problem, and developed a method to fabricate ferroelectric nylon thin-film capacitors by dissolving nylon in a mixture of trifluoroacetic acid and acetone and solidifying it again in vacuum. They were able to understand thin nylon films that were typically only a few 100 nanometers thick, several 100 times thinner than human hair. “Using this method, we have produced extremely smooth thin films. This is very important because it prevents electrical break down of for example capacitors and destroying the electronic circuits. At the same time, smoothness allows for transparent thin films and eventually transparent electronic devices. ”Says Dr. Kamal Asadi, group leader at the MPI-P.

By using their newly developed method, the group around Kamal Asadi was able to produce high-performance nylon capacitors. The scientists are subjected to the prototypes of capacitors for extended stress cycles and the demonstrated robustness of ferroelectric nylons under millions of operation cycles. Thin nylon films could become an important component for use in flexible electronics in the future and find applications in bendable electronic devices or for electronics in clothing. These new findings pave the way toward multi-functional fabrics that serve as a cloth to cover our body and at the same time can generate electricity from our body movement.

Their results have now been published in the renowned journal Science Advances.