New biodegradable structures could improve energy, information technologies and help to advance medicine. This is in the form of soft, sustainable electroactive materials. This follows Northwestern University researchers designing new materials using peptides and tiny molecular segments found in plastics.
The process results in a soft material with ferroelectric and piezoelectric properties. This material requires extremely low energy to switch its polarity, unlocking applications in sustainable energy and information storage. Another application is with low-power, energy-efficient microscopic memory chips, sensors and energy storage units
In terms of other practical use, arrays of fibres containing the new materials could be woven together into smart fabrics, medical implants or wearable devices. As an example, this could include new types of ultralight electronic devices while reducing the environmental impact of electronic manufacturing and disposal. Manufacturers could integrate the material into woven fibres to create smart fabrics or sticker-like medical implants.
The materials are made of tiny, flexible nano-sized ribbons that can be charged just like a battery to store energy or record digital information.
According to lead researcher Samuel I. Stupp: “This is a wholly new concept in materials science and soft materials research. We 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.”
Stupp adds: “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.”
The basis of the new material is peptide amphiphiles. This is 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.
The scientists replaced the lipid tail with a miniature molecular segment of a plastic called polyvinylidene fluoride (PVDF). However, they kept the peptide segment, which contains sequences of amino acids.
Commonly used in audio and sonar technologies, PVDF is a plastic with special 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. The new materials are equally ferroelectric and piezoelectric as PVDF, and the electroactive forms are stable, with the ability to switch polarity using extremely low external voltages. This makes them suitable for low-power electronics
The research has been published in the journal Nature, titled “Peptide programming of a supramolecular vinylidene fluoride ferroelectric phase.”
