Have flexible, transient and biodegradable electronics finally arrived?

The ACS Applied Nano Materials cover illustrates a new approach for creating helix-rich RSF films based on molecular interactions between the protein molecules and carboxyl-functionalized surfaces of a small quantity of added carbon nanotubes (CNTs). Local heating of CNTs using microwave irradiation (depicted here as glowing red) then leads to the formation of helical conformations in fibroins near the CNTs. (Randall McKenzie/McKenzie Illustrations)

Pitt researchers find that nanotube interactions with silk fibroins hold the key to developing flexible, degradable electronics

The silk fibers produced by Bombyx mori, the domestic silkworm, has been prized for millennia as a strong yet lightweight and luxurious material. Although synthetic polymers like nylon and polyester are less costly, they do not compare to silk’s natural qualities and mechanical properties. And according to research from the University of Pittsburgh’s Swanson School of Engineering, silk combined with carbon nanotubes may 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 Oct. 26 cover of the American Chemistry Society journal Applied Nano Materials.

“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 the paper. “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.”

As explained by the authors in the video below, these regenerated silk fibroins (RSFs) however typically are chemically unstable in water and suffer from inferior mechanical properties, owing to the difficulty in precisely controlling the molecular structure of the fibroin proteins in RSF films.  Bedewy and his NanoProduct Lab group, which also work extensively on carbon nanotubes (CNTs), thought that perhaps the molecular interactions between nanotubes and fibroins could enable “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 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.”

According to Dr. Bedewy, the microwave irradiation, coupled with a solvent vapor treatment, provided a unique control mechanism for the protein structure and resulted in a flexible and transparent film comparable to synthetic polymers but one that could be both more sustainable and degradable. These RSF-CNT films have potential for use in flexible electronics, biomedical devices and transient electronics such as sensors that would be used for a desired period inside the body ranging from hours to weeks, and then naturally dissolve.

“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.”

Learn more: Making a Transparent Flexible Material of Silk and Nanotubes

 

 

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Tomorrow’s degradable electronics

Electronic circuits can be implanted into surgical wounds and assist the healing process by accelerating wound closure. After a few weeks, the electronics are dissolved by the body fluids, making it unnecessary to re-open the wound to remove them manually. Photos: Werner Juvik/SINTEF - See more at: http://gemini.no/en/2014/11/tomorrows-degradable-electronics/#sthash.7yxFWZ7H.dpuf

Electronic circuits can be implanted into surgical wounds and assist the healing process by accelerating wound closure. After a few weeks, the electronics are dissolved by the body fluids, making it unnecessary to re-open the wound to remove them manually. Photos: Werner Juvik/SINTEF

Norwegian researchers are developing electronics that disappear to order.

When the FM frequencies are removed in Norway in 2017, all old-fashioned radios will become obsolete, leaving the biggest collection of redundant electronics ever seen – a mountain of waste weighing something between 25,000 and 30,000 tonnes.

The same thing is happening with today’s mobile telephones, PCs and tablets, all of which are constantly being updated and replaced faster than the blink of an eye. The old devices end up on waste tips, and even though we in the west recover some materials for recycling, this is only a small proportion of the whole.

And nor does the future bode well with waste in mind. Technologists’ vision of the future is the “Internet of Things”. Electronics are currently printed onto plastics. All products are fitted with sensors designed to measure something, and to make it possible to talk to other devices around them. Davor Sutija is General Manager at the electronics firm Thin Film, and he predicts that in the course of a few years each of us will progress from having a single sensor to having between a hundred and a thousand. This in turn will mean that billions of devices with electronic bar codes will be released onto the market.

No time to lose

Researchers are now getting to grips with this problem. Their aim is to develop processes in which electronics are manufactured in such a way that their entire life cycle is controlled, including their ultimate disappearance.

In New Orleans in the USA, researchers have made electronic circuits which they implant into surgical wounds following operations on rats. Each wound is sewn up and the electricity in the circuits then accelerates the healing process. After a few weeks, the electronics are dissolved by the body fluids, making it unnecessary to re-open the wound to remove them manually.

In Norway, researchers at SINTEF have now succeeded in making components containing magnesium circuits designed to transfer energy. These are soluble in water and disappear after a few hours.

A demanding process

“We make no secret of the fact that we are putting our faith in the research results coming out of the USA”, says Karsten Husby at SINTEF ICT. “The Americans have made amazing contributions both in relation to medical applications, and towards resolving the issue of waste. We want to try to find alternative approaches to the same problem”, he says.

Read more . . .  

 

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