To keep getting faster, electronics must eventually shrink down to the nanoscale. But making wires and switches that small is no easy feat. Biological molecules, with their ability to self-assemble, offer one promising approach. In research done at the University of Chicago, scientists have engineered proteins to form cores for gold wires only 80 nanometers wide.
The researchers started with yeast prions-harmless cousins of the proteins that cause mad-cow disease. Under certain conditions, these prions spontaneously form highly stable fibrils. The team genetically engineered the fibrils to bind tightly to specially prepared gold nanoparticles. The result was fibrils dotted with gold blobs. To fill gaps between the blobs, the team added silver and then more gold, producing conducting wires. “One can imagine using them to build small-scale circuitry for computers, biosensors-there’s a whole world of things,” says geneticist Susan Lindquist, who collaborated on the project with physicist Heinrich Jaeger in Chicago and is now director of MIT’s Whitehead Institute for Biomedical Research. The work was described this spring in the Proceedings of the National Academy of Sciences.
The prions have advantages over other biological molecules that researchers have so far tried to use for nanoelectronics. Merging silver with DNA, for example, has allowed scientists to make nanowires, which, thanks to DNA’s ability to specifically bind to complementary sequences, can then form circuitlike patterns. But the weak bonds between DNA strands tend to break easily. This is less of a problem for protein fibrils. “We think that proteins offer a whole realm of different capabilities,” Lindquist says. Indeed, creating self-assembling nanostructures from proteins “is a very exciting area,” says Chris Dobson, a structural biologist at the University of Cambridge in England. His lab is using protein fibrils to build electronic materials and optical materials for telecommunications.
In collaboration with MIT materials chemist Angela Belcher, Lindquist’s group is already extending the work. Belcher’s lab has developed proteins that can bind to about 30 different electronic, magnetic, and optical materials, and then assemble the materials into structures. The goal is to integrate Belcher’s proteins into Lindquist’s self-assembly system to create a way to “grow” materials-such as semiconductors-where and in whatever patterns the researchers want. Though it’s impossible to predict how long it might take for the new techniques to make their way into industrial use, the research is setting a firm foundation for practical nanotechnology.