Scientists have developed materials made of tiny, flexible nano-sized ribbons that can be charged just like a battery to store energy or record digital information.
Developed by researchers from Northwestern University, the highly energy efficient, biocompatible and made from sustainable materials could give rise to new types of ultralight electronic devices while reducing the environmental impact of electronic manufacturing and disposal.
Published in the journal Nature, the study mentions that the new soft materials could be used in low-power, energy-efficient microscopic memory chips, sensors and energy storage units.
Materials could also be integrated into woven fibers
Researchers maintain that these materials could also be integrated into woven fibers to create smart fabrics or sticker-like medical implants. In today’s wearable devices, electronics are clunkily strapped to the body with a wristband. But, with the new materials, the wristband itself could have electronic activity.
Northwestern’s Samuel I. Stupp, who led the study, stated that this is a wholly new concept in materials science and soft materials research.
Stupp maintained that researchers imagine a future where you could wear a shirt with air conditioning built into it or rely on soft bioactive implants that feel like tissues and are activated wirelessly to improve heart or brain function.
“Those uses require electrical and biological signals, but we cannot build those applications with classic electroactive materials. It’s not practical to put hard materials into our organs or in shirts that people can wear. We need to bring electrical signals into the world of soft materials. That is exactly what we have done in this study,” added Stupp.
Secret behind the new material is peptide amphiphiles
Researchers maintained that the secret behind the new material is peptide amphiphiles, a versatile platform of molecules previously developed in Stupp’s laboratory. These self-assembling structures form filaments in water and have already demonstrated promise in regenerative medicine. The molecules contain peptides and a lipid segment, which drives the molecular self-assembly when placed in water.
In the new study , the team replaced the lipid tail with a miniature molecular segment of a plastic called polyvinylidene fluoride (PVDF). But they kept the peptide segment, which contains sequences of amino acids. Commonly used in audio and sonar technologies, PVDF is a plastic with unusual electrical properties.
It can generate electrical signals when pressed or squeezed — a property known as piezoelectricity. It also is a ferroelectric material, which means it has a polar structure that can switch orientation by 180 degrees using an external voltage. The dominant ferroelectrics in technology are hard materials and often include rare or toxic metals, such as lead and niobium .
Stupp stated that PVDF was discovered in the late 1960s and is the first known plastic with ferroelectric properties.
“It has all the robustness of plastic while being useful for electrical devices. That makes it a very high-value material for advanced technologies. However, in pure form, its ferroelectric character is not stable, and, if heated above the so-called Curie temperature, it loses its polarity irreversibly,” said Stupp.
All plastics, including PVDF, contain polymers, which are giant molecules typically composed of thousands of chemical structural units. In the new study, the Stupp laboratory precisely synthesized miniature polymers with only 3 to 7 vinylidene fluoride units. Interestingly, the miniature segments with 4, 5 or 6 units are programmed by nature’s beta-sheet structures, which are present in proteins, to organize into a stable ferroelectric phase, according to the study .
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