New Material: Researchers Have Developed The Technology Of Creating Two-Dimensional Silk Protein Layer On Graphene

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Researchers have developed a method to create a two-dimensional silk protein layer on graphene, thus improving the application potential of graphene in the field of microelectronics, especially in wearable and implantable health sensors and storage transistors in the field of computing. This innovation provides a non-toxic, water-based and bio compatible system, which may completely change the application of silk in luxury materials and high-tech industries. This research has opened the way for further promoting silk integrated circuits and sustainable electronic solutions.

A single silk protein molecule or "silk fibroin" (blue) is deposited on the surface of graphene, surrounded by water (green and red spheres), and grown into atomic precision two-dimensional (2D) sheets. The controllable deposition of silk fiber may bring a large number of biodegradable electronic devices. Source: Mike Perkins | Pacific Northwest National Laboratory

For thousands of years, silk has been a valuable commodity, but it still brings surprises to people. Now, it may help to create a new direction in microelectronics and computing.

Although silk protein has been used in the design of electronic products, its application is still limited, partly because silk fiber is a messy spaghetti fiber.

Now, a research team led by scientists from the U.S. Department of Energy's Northwest Pacific National Laboratory (PNNL) has tamed this tangle. Today (September 18), they are writing in Science Advanced magazine reported that they have formed a uniform two-dimensional (2D) silk protein fragment (or "fibrin") layer on graphene, a carbon based material with excellent electrical conductivity.

Atomic force microscope image of silk cellulose uniformly self-assembled on graphene. Photo source: James De Yoreo | Pacific Northwest National Laboratory

"These results provide a repeatable silk protein self-assembly method, which is crucial for designing and manufacturing silk based electronic devices," said Shi Chenyang, the first author of the study. "It is worth noting that this system is non-toxic and water-based, which is crucial for biological compatibility."

This combination of materials -- silicon on graphene -- can form a sensitive and adjustable transistor, which is a wearable and implantable health sensor very needed by the microelectronics industry. PNNL The team also saw their potential as key components of memory transistors or "memristors" for computing neural networks. The memristor used in the neural network can let the computer imitate the operation of the human brain.

For centuries, silk production has been a closely guarded secret in China, and its reputation spread to India, the Middle East, and finally to Europe through the famous Silk Road trade routes. By the Middle Ages, silk had become a symbol of identity and a coveted commodity in the European market. Today, silk is still associated with luxury and status.

Silk fabrics are famous all over the world for their elasticity, durability, strength and other basic characteristics, and are widely used in the field of advanced materials.

James De Yoreo, PNNL Bartel researcher, professor of materials science and engineering and professor of chemistry at Washington University Said: "There have been many studies on the use of silk to modulate electronic signals, but due to the natural disorder of silk proteins, only limited control can be carried out. Therefore, with our experience in controlling the surface growth of materials, we are thinking, 'What if we can create a better interface?'"

For this reason, the research team carefully controlled the reaction conditions and added a single silk fiber into the water-based system in an accurate way. Through precise laboratory conditions, the research team has obtained a highly ordered two-dimensional protein layer. These proteins are arranged in precise parallel beta sheets, which is one of the most common protein shapes in nature. Further imaging studies and supplementary theoretical calculations show that the filament layer adopts a stable structure and has the characteristics of natural silk. The electronic structure of this scale is less than Half of the DNA strand supports the miniaturization seen everywhere in the bioelectronics industry.

　　De Yoreo Said, "This material itself has what we call the field effect. This means that it is a transistor switch that can be turned on or off according to the signal. If you add antibodies to it, when the target protein binds, it will cause the transistor to switch over."

In fact, researchers are planning to use this starting material and technology to produce their own rayon, and add functional proteins in it to improve its practicality and specificity.

This research has taken the first step of controllable layering of silk on functional electronic components. The key areas of future research include improving the stability and conductivity of silk integrated circuits, and exploring the potential of silk in biodegradable electronic products, so as to make more use of green chemistry in electronic manufacturing.