Flexible, eco-friendly electronic plastic for wearable tech, sensors

CLEVELAND—Researchers at Case Western Reserve University have developed an environmentally safer type of plastic that can be used for wearable electronics, sensors and other electrical applications.

The material, a so-called ferroelectric polymer, is made without fluorine, considered a “forever” chemical that hurts the environment because compounds made with it don’t break down quickly or at all.

Although the researchers are still working to improve the material’s electric and elastic properties, the potential is vast for its flexibility of electronic uses and eco-friendly structure.

“How this material generates its electric properties is also fundamentally new,” said lead researcher Lei Zhu, a professor of macromolecular science and engineering at the Case School of Engineering. “Unlike current ferroelectric materials, it doesn’t have to crystallize to lock in the polarity that gives it electrical properties.”

The research explaining the discovery was recently published in the journal Science. The new material is patent pending.

Electronic polymers

Polymers are large molecules comprised of long chains of smaller molecular units that can be man-made—such as plastics—or natural—like in a person’s hair or DNA. By changing a polymer’s molecular structure and length, it can vary its strength, flexibility, heat-resistance and ability to be recycled.

Ferroelectricity refers to certain materials with what is known as “spontaneous polarization” that can be reversed by applying an electric field—like an on-off switch. Ferroelectric materials allow for the development of smaller, more efficient electronic devices, reducing our reliance on traditional energy sources.

Flexible on-off switches

The new material Zhu and his research team have created is both flexible and has what is known as tunable electronic properties, which means they can be switched on and off.

They have wide applications in infrared detectors and sensors in wearable electronics, for which the materials need to be soft, pliable and elastic to be compatible with the human body. Conventional ceramic ferroelectric materials are rigid and brittle.

Polymers have the advantage of being flexible and lightweight, but the dominant ferroelectric polymer, poly(vinylidene fluoride), or PVDF, doesn’t naturally degrade in the environment, making it a “forever chemical.” The new material is made without fluorine.

Ferroelectric polymers also have applications in sensors for ultrasound diagnostic tools because they are acoustically compatible with biological tissues. They are also potentially useful in augmented and virtual reality (AR and VR) goggles.

The research was supported with a research grant from the U.S. Department of Energy in 2017. When the grant funding expired in 2022, the researchers kept working on it, until finally they “hit the jackpot,” Zhu said.

“We’re still in the development stage of synthesizing small quantities and investigating the properties,” he added. “But we’re excited about the potential to replace environmentally harmful plastics in sensors and detectors.”

The research team includes: from Case Western Reserve, Philip Taylor, the Perkins Professor of Physics Emeritus, Elshad Allahyarov, visiting professor of physics, Jiahao Huang, research associate in macromolecular science and engineering; and researchers from Penn State University, Vanderbilt University, Brookhaven National Laboratory, Tennessee State University and the University of Tennessee at Knoxville.

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