An illustration showing silk protein fragments depositing on graphene. Mike Perkins/Pacific Northwest National Laboratory
A team of international researchers has developed tunable transistors using silk and graphene. Tunable transistors are components found in circuits of various electronic and computing devices.
Their primary role is to enable real-time adjustments in a circuit’s performance, allowing it to optimize its functions according to changing conditions, such as signal strength, frequency, or environmental factors.
Tunable transistors are found in a variety of devices ranging from smartphones to radar systems and quantum computing applications. However, they are typically made of silicon, a material that doesn’t break down easily and contributes to the growing e-waste problem.
In their new study, the researchers show that silk can solve this problem as it has the potential to enable the development of biodegradable electronic devices.
The trick to turning silk protein into a transistor
Silk is well-known for its durability, elasticity, and strength, and this is why scientists in different corners of the world have been trying to use this material in hi-tech applications.
However, silk proteins are naturally disordered, acting like messed-up entangled spaghetti strands, which is why integrating them into electronics is challenging.
“There’s been a lot of research using silk as a way of modulating electronic signals, but because silk proteins are naturally disordered, there’s only so much control that’s been possible,” James De Yoreo, one of the study authors, said.
To overcome this challenge, the study authors used graphene as the base, and upon it, carefully arranged uniform 2D layers of silk protein fragments, also called fibroins. Graphene prevents fibroins from disorganizing, allowing better control over the signals transmitted through them.
This entire setup is then packed in the form of β-sheets (a common protein shape). When they tested this arrangement, it demonstrated properties similar to that of a stable tunable transistor.
“This type of material lends itself to what we call field effects. This means that it’s a transistor switch that flips on or off in response to a signal. If you add, say, an antibody to it, then when a target protein binds, you cause a transistor to switch states.” De Yoreo said.
“It’s important to note that this system is non-toxic and water-based, which is crucial for biocompatibility,” Chenyang Shi, lead author of the study, added.
The use of silk is not limited to one component
Humans are producing over 60 million tonnes of electronic waste annually, and this number is only increasing with each passing year. Currently, the world doesn’t have the manpower and resources to process and recycle even half of this waste.
Moreover, non-biodegradable materials from used circuit boards, such as silicon, are making the e-waste problem more complex because once discarded, they remain in the environment for hundreds of years if not picked up for recycling.
This is why, our world is in dire need of biodegradable electronics and although we can’t entirely replace silicone from electronics, the development of silk-based circuit components is a big achievement. The current study “represents the first step in controlled silk layering on functional electronic components.”
According to the researchers, the next step would be to add other types of protein to the silk-graphene material to improve its properties. Plus, they plan to develop different types of artificial silk using the current material.
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They believe the use of silk in electronics is not limited to making transistors. The insights from their study could help scientists in making biodegradable versions of various other hi-tech circuit components, such as memristors, using silk.
“These results provide a reproducible method for silk protein self-assembly that is essential for designing and fabricating silk-based electronics,” Shi said.
The study is published in the journal Science Advances.
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