Using peptides and components from large plastic molecules, materials scientists have created small, adaptable nano-sized ribbons that function like batteries by storing energy or logging digital data.
Forget about stiff and unyielding materials. A new softer, eco-friendly electroactive material is making waves — and it’s set to revolutionize medical devices, wearable tech, and the way we interact with computers.
Researchers at Northwestern University, applying peptides and fragments of large plastic molecules, have crafted materials from tiny, flexible nano-sized ribbons that can be charged similarly to batteries to either save energy or capture digital information. These materials are highly energy-efficient, biocompatible, and produced from sustainable resources. They could lead to ultralight electronic gadgets while minimizing the environmental footprint associated with electronic production and disposal.
The findings of this research will be published on October 9 in the journal Nature.
With more advancement, these new flexible materials have the potential to be used in low-power, energy-efficient microscopic memory chips, sensors, and energy-storing devices. Researchers could also integrate these materials into woven fabrics, paving the way for smart fabrics or adhesive medical implants. Currently, in today’s wearable technology, electronics are awkwardly attached via wristbands. However, with these new materials, the wristband itself could incorporate electronic functions.
“This represents an entirely new concept in materials science and research into soft materials,” stated Northwestern’s Samuel I. Stupp, who led the research. “We envision a future where shirts could have built-in air conditioning or soft bioactive implants that mimic tissues and can be activated wirelessly to enhance heart or brain functionality.
“These applications necessitate the use of electrical and biological signals, but traditional electroactive materials cannot support them. It’s impractical to introduce rigid materials into our organs or in garments that people wear. We need to integrate electrical signals into soft materials, and that is precisely what we achieved in this research.”
Stupp is the Board of Trustees Professor of Materials Science and Engineering, Chemistry, Medicine, and Biomedical Engineering at Northwestern. He has also been the director of the U.S. Department of Energy-supported Center for Bio-Inspired Energy Science for over a decade, where this research originated. Yang Yang, a research associate in Stupp’s lab, is the first author of the paper.
Peptides and plastics combine for real innovation
The core of this groundbreaking material lies in peptide amphiphiles, a versatile molecule framework previously crafted in Stupp’s lab. These self-assembling structures create filaments in water and have shown promise in regenerative medicine. The molecular design includes peptides and a lipid fragment, which promotes the self-assembly process in water.
In this study, the team substituted the lipid tail with a small molecular piece from a plastic called polyvinylidene fluoride (PVDF). However, they retained the peptide segment that consists of amino acid sequences. PVDF is commonly used in audio and sonar applications and possesses unique electrical properties, generating electrical signals when compressed or stretched—a feature known as piezoelectricity. It is also a ferroelectric material, which means it can alter its polar orientation using an external voltage. Most existing ferroelectric materials are solid and often incorporate rare or harmful metals like lead and niobium.
“PVDF was discovered in the late 1960s and is the first plastic identified with ferroelectric characteristics,” remarked Stupp. “It combines the durability of plastic with its electrical utility, making it a valuable material for advanced technologies. However, in its pure form, its ferroelectric stability is not reliable, and if it exceeds a certain temperature known as the Curie temperature, it permanently loses its polarity.”
All plastics, including PVDF, are composed of polymers—large molecules made of thousands of chemical building blocks. In this research, Stupp’s team precisely created miniature polymers containing only 3 to 7 vinylidene fluoride units. Notably, the miniature segments with four, five, or six units are naturally organized into a stable ferroelectric state, thanks to the beta-sheet structures found in proteins.
“Achieving this was not simple,” Stupp noted. “The unexpected partnership of peptides and plastics led to significant breakthroughs.”
The new materials exhibited ferroelectric and piezoelectric properties similar to PVDF, and their electroactive forms proved stable, able to switch polarity with very low external voltages. This paves the way for energy-efficient electronics and sustainable nanoscale devices. The researchers also foresee the development of innovative biomedical technologies by attaching bioactive signals to the peptide segments, a method that has been successfully utilized in Stupp’s regenerative medicine research. This combines the unique attributes of electrically active materials with bioactive characteristics.
The magic of water
To form these sustainable structures, Stupp’s team merely added water to initiate the self-assembly process. After soaking the materials, Stupp was astonished to discover that they showcased the highly desired ferroelectric properties of PVDF.
In response to an external electric field, ferroelectric materials shift their polar orientation, akin to flipping a magnet from north to south and back again. This trait is crucial for constructing information-storage devices, a vital component for artificial intelligence solutions. Surprisingly, the researchers found that “mutations” in the peptide sequence could adjust properties related to ferroelectricity or even convert the structures into ideal materials for acting or storing energy, known as “relaxor phases.”
“In biological contexts, mutations in peptide sequences can lead to diseases or biological advantages,” Stupp explained. “In our new materials, we mutate peptides to adjust their characteristics for practical applications.
“With nanoscale electrodes, we could expose a vast number of self-assembling structures to electric fields. We could effortlessly flip their polarity with low voltage, designating one position as a ‘one’ and the opposite as a ‘zero.’ This creates binary codes for data storage. Moreover, these materials are ‘multiaxial’, meaning they can develop polarity in various directions rather than just one or two specific ones.”
Unmatched low power
Unlike traditional soft ferroelectric materials such as PVDF, which require significant external electric fields to change polarity, these new structures demand remarkably low voltage.
“The energy needed to reverse their polarity is the lowest documented for multiaxial soft ferroelectrics,” Stupp stated. “This could significantly conserve energy in our increasingly high-demand world.”
Additionally, these new materials come with inherent environmental advantages. Unlike typical plastics that can persist in the environment for centuries, the materials developed by Stupp’s lab could be biodegradable or repurposed without reliance on harmful, toxic solvents or high-energy processes.
“We are presently exploring unconventional applications for ferroelectrics that include biomedical devices and implants, as well as catalytic processes crucial for renewable energy,” Stupp said. “Due to the use of peptides in our new materials, they can be functionalized with biological signals. We are eagerly anticipating these new developments.”
