Silk And Nanotubes Make Flexible Electronics

Scientists are taking advantage of the natural properties of silk to open doors into biodegradable sensors.

Silk has fascinated humans for centuries. A waste product of silkworms, silk is a natural fiber with incredible properties like softness and strength.

Synthetic alternatives have been developed such as nylon and polyester. However, none of them come close to the brilliance of silk. This luxurious material has now caught the eye of scientists who believe it could be the key to a new generation of biomedical devices including biodegradable electronics.

Natural fibers useful for advanced biomedical applications

Researchers from research from the University of Pittsburgh Swanson School of Engineering, are exploring combining silk with carbon nanotubes “Silk is a very interesting material. It is made of natural fibers that humans have been using for thousands of years to make high-quality textiles, but we as engineers have recently started to appreciate silk’s potential for many emerging applications such as flexible bioelectronics due to its unique biocompatibility, biodegradability, and mechanical flexibility,” noted Mostafa Bedewy, assistant professor of industrial engineering at the Swanson School and lead author of a new research paper.

The scientists need to change the silk from its naturally occurring fibers into silk proteins. “The issue is that if we want to use silk for such applications, we don’t want it to be in the form of fibers. Rather, we want to regenerate silk proteins, called fibroins, in the form of films that exhibit desired optical, mechanical and chemical properties,” Bedewy says.

Researchers will continue to explore the potential of silk in wearables

However, these regenerated silk fibroins (RSFs) are generally unstable in water and have less mechanical properties than natural silk due to the difficulty in precisely controlling the molecular structure of the fibroin proteins in RSF films. To overcome this hurdle Bedewy and his NanoProduct Lab group, are experimenting with the molecular interactions between nanotube and fibroins could enable “tuning” the structure of RSF proteins.

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“One of the interesting aspects of CNTs is that, when they are dispersed in a polymer matrix and exposed to microwave radiation, they locally heat up,” Dr. Bedewy explained. “So we wondered whether we could leverage this unique phenomenon to create desired transformations in the fibroin structure around the CNTs in an “RSF-CNT” composite.”

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According to the researchers, the combination of the microwave irradiation and the solvent vapor treatment helped create a control mechanism for the protein structure and resulted in a flexible and transparent film. The new film is similar to synthetic polymers but is more sustainable and degradable. “We are excited about advancing this work further in the future, as we are looking forward to developing the science and technology aspects of these unique functional materials,” Dr. Bedewy said.

“From a scientific perspective, there is still a lot more to understand about the molecular interactions between the functionalization on nanotube surfaces and protein molecules. From an engineering perspective, we want to develop scalable manufacturing processes for taking cocoons of natural silk and transforming them into functional thin films for next-generation wearable and implantable electronic devices.”

The research team will continue to develop these process to unlock their potential for use in flexible electronics, biomedical devices and transient electronics such as sensors.

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The study, “Promoting Helix-Rich Structure in Silk Fibroin Films through Molecular Interactions with Carbon Nanotubes and Selective Heating for Transparent Biodegradable Devices” was featured on the Oct. 26 cover of the American Chemistry Society journal Applied Nano Materials.

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