Making a Transparent Flexible Material of Silk and Nanotubes

The silk fibers produced by Bombyx mori, the domestic silkworm, has been prized for millennia. Although synthetic polymers like nylon and polyester are less expensive, they do not compare to silk's natural qualities and mechanical properties. And according to the University of Pittsburgh's Swanson School of Engineering, nanotubes can lead to a new generation of biomedical devices and so-called transient, biodegradable electronics.

The study, "Promoting Helix-Rich Structure in Silk Fibroin Films through Molecular Interactions with Carbon Nanotubes and Selective Heating for Transparent Biodegradable Devices" (DOI: 10.1021 / acsanm.8b00784), was featured on the October 26 cover of the American Chemistry Society journal Applied Nano Materials.

"Silk is a very interesting material, but it is made of natural fibers that it is made of high quality textiles, but we as engineers its unique biocompatibility, biodegradability and mechanical flexibility, "noted Mostafa Bedewy, assistant professor of industrial engineering at the Swanson School and lead author of the paper. Rather, we want to regenerate silk proteins, called fibroins, in the form of films , mechanical and chemical properties. "

As explained by the authors, these regenerated silk fibroins (RSFs), however, are typically unstable in water and fibrosis, and can be described in the following table. NanoProduct Lab Group, which also work extensively on carbon nanotubes (CNTs), thought that the molecular interactions between nanotubes and fibroins could be "tuning" the structure of RSF proteins.

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

According to Dr. Bedewy, the microwave irradiation, coupled with a flexible vapor treatment, provided a unique control mechanism for the protein structure and resulted in a flexible and transparent film comparable to synthetic polymers that could be both more sustainable and degradable. These RSF-CNT films have potential for use in flexible electronics, biomedical devices, and transient electronics as they would be used for a naturally occurring device.

"We are excited about advancing this work further in the future," said Dr. Bedewy said. "From a scientific perspective, there is 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. "