After 1000’s of years as a highly priceless commodity, silk continues to surprise. Now it might help usher in a complete recent direction for microelectronics and computing.
While silk protein has been deployed in designer electronics, its use is currently limited partially because silk fibers are a messy tangle of spaghetti-like strands.
Now, a research team led by scientists on the Department of Energy’s Pacific Northwest National Laboratory has tamed the tangle. They report within the journal Science Advances that they’ve achieved a uniform two-dimensional (2D) layer of silk protein fragments, or “fibroins,” on graphene, a carbon-based material useful for its excellent electrical conductivity.
“These results provide a reproducible method for silk protein self-assembly that is crucial for designing and fabricating silk-based electronics,” said Chenyang Shi, the study’s lead writer. “It is vital to notice that this technique is nontoxic and water-based, which is crucial for biocompatibility.”
This mix of materials — silk-on-graphene — could form a sensitive, tunable transistor highly desired by the microelectronics industry for wearable and implantable health sensors. The PNNL team also sees potential for his or her use as a key component of memory transistors or “memristors,” in computing neural networks. Memristors, utilized in neural networks, allow computers to mimic how the human brain functions.
The Silk Road
For hundreds of years, silkworm silk production was a closely guarded secret in China, while its fame spread through the celebrated Silk Road trade routes to India, the Middle East, and eventually Europe. By the Middle Ages, silk had change into a standing symbol and a coveted commodity in European markets. Even today, silk is related to luxury and standing.
The identical underlying properties that make silk fabric world-renowned — elasticity, durability, and strength — have led to its use in advanced materials applications.
“There’s been numerous research using silk as a way of modulating electronic signals, but because silk proteins are naturally disordered, there’s only a lot control that is been possible,” said James De Yoreo, a Battelle Fellow at PNNL with a dual appointment as a Professor of Materials Science and Engineering and of Chemistry on the University of Washington. “So, with our experience in controlling material growth on surfaces, we thought ‘what if we will make a greater interface?'”
To do this, the team fastidiously controlled the response conditions, adding individual silk fibers to the water-based system in a precise manner. Through precision laboratory conditions, the team achieved a highly organized 2D layer of proteins packed in precise parallel β-sheets, one of the vital common protein shapes in nature. Further imaging studies and complementary theoretical calculations showed that the skinny silk layer adopts a stable structure with features present in natural silk. An electronic structure at this scale — lower than half the thickness of a strand of DNA — supports the miniaturization found in all places within the bio-electronics industry.
“Such a material lends itself to what we call field effects,” said De Yoreo. “Because of this it is a transistor switch that flips on or off in response to a signal. In case you add, say, an antibody to it, then when a goal protein binds, you cause a transistor to change states.”
Indeed, the researchers are planning to make use of this starting material and technique to create their very own artificial silk with functional proteins added to it to reinforce its usefulness and specificity.
This study represents step one in controlled silk layering on functional electronic components. Key areas of future research include improving the steadiness and conductivity of silk-integrated circuits and exploring silk’s potential in biodegradable electronics to extend the usage of green chemistry in electronic manufacturing.
Along with De Yoreo, PNNL materials scientist Shuai Zhang and Xiang Yang Liu of Xiamen University, Xiamen, China, were co-lead authors of the study. Other contributors include Marlo Zorman of the University of Washington, Seattle; Xiao Zhao and Miquel B. Salmeron of Lawrence Berkeley National Laboratory; and Jim Pfaendtner of North Carolina State University.
This study was supported by the DOE Office of Science, Basic Energy Sciences program. The molecular dynamics simulations and scanning Kelvin probe microscopy measurements were supported by the DOE BES Energy Frontiers Research Centers program through CSSAS: The Center for the Sciences of Synthesis Across Scales on the University of Washington.
