Flexible devices are a step closer

Photo credit: YoungPak Lee/ Hanyang University Image shows nanoparticles of bismuth ferrite embedded in a polymer film. The film enhances the electric and magnetic properties of bismuth ferrite, and preservers these properties, even when the film is bent.
Researchers from South Korea have manufactured a thin film that keeps its electric and magnetic properties even when it is curved.

For wearable technology, a truly flexible electronic device is the goal. One that can wrap around limbs as the wearer exercises, or a computer that can be folded up and carried on your person.

This electron microscope image shows tiny nanoparticles of bismuth ferrite embedded in a polymer film. The film enhances the unique electric and magnetic properties of bismuth ferrite and preserves these properties even when bent.

The researchers describe the film in a paper published in Applied Physics Letters, AIP Publishing.

Flexible electronics have been hard to manufacture because many materials with useful electronic properties tend to be rigid. Researchers have addressed this problem by taking tiny bits of materials like silicon and embedding them in flexible plastics.

A team of physicists and engineers from South Korea took the conventional approach of flexible design, whereby manufacturers take tiny pieces of material, e.g. silicon, and embed them in flexible plastics. The team used bismuth ferrite (BiFeO3). This material's electronic properties can be controlled by a magnetic field.

The researchers synthesized nanoparticles of bismuth ferrite and mixed them into a polymer solution. The solution was dried in a series of steps at increasing temperatures, to produce a thin, flexible film.

When the researchers tested the electric and magnetic properties of the film they found that their new material not only preserved, but improved the properties of bulk bismuth ferrite. Furthermore, the improved properties remained even as the film was curved into a cylindrical shape.

"Bulk bismuth ferrite has crucial problems for some applications, such as a high leakage current which hinders the strong electric properties," said YoungPak Lee, a professor at Hanyang University in Seoul, South Korea. Mixing nanoparticles of bismuth ferrite into a polymer improved the current-leakage problem and also gave the film flexible, stretchable properties.

Multi-ferroric materials such as this could be used in high-density, energy efficient memory and switches in wearable devices.

Caroline Hayes

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