The nanowire transistors maintain their state-on or off—regardless of whether the power is on. This gives it an instant-on capability, important for low-power sensors that might need to collect data only sporadically and also need to conserve power.
According to Das, the circuits could also be 10 times more power-efficient than circuits made of traditional materials. One reason is the nanowire’s electrical properties, which don’t allow electric current to leak, unlike traditional transistors. Another reason is that the circuit design uses capacitive connections instead of resistive ones, which are less efficient. “We don’t burn a lot of power driving resistors,” says Das.
“This is a significant milestone on several fronts,” says André DeHon, professor of electrical and system engineering at the University of Pennsylvania. Reprogrammable transistors made of nanowires are “the building block I was hoping for,” he says.
The researchers’ work represents “a leap forward in complexity and function of circuits built from the bottom up,” says Zhong Lin Wang, professor of materials science and engineering at Georgia Institute of Technology. It shows that the bottom-up method for manufacturing “can yield nanoprocessors and other integrated systems of the future,” he says.
More work needs to be done to make nanowire processors practical for use in electronics systems, Lieber says. His group needs to demonstrate thousands of transistors on a tile—many times more than the current 496 transistors his group has so far achieved. In addition, they need to scale up to multiple tiles. The researchers are in the process of finding the best way to link a 16-tile system together. Lieber says that, realistically, manufacturing these circuits is still several years down the road.