The device consists of a chip containing an array of silicon nanowires coated with an organic amine compound that binds to the explosives, changing the wires’ conductance. Patolsky says the trick is to grow nanowires at desired spots and along a defined direction on the chip. Once the array is grown, the researchers coat the nanowires and deposit the electrodes. In laboratory tests, the chip was exposed to liquid solutions containing explosives, as well as to TNT vapors mixed with air. The researchers are working on packaging the chip with microfluidics pumps and electronics to make a low-power, portable detector.
Aimee Rose, a researcher at ICx Technologies, says that using nanowire arrays for sensing shows great promise because the method is so sensitive, allowing potential developers to “put many sensors in a small footprint,” but the method will have to prove its mettle with real-world vapor samples.
MIT chemistry professor Timothy Swager agrees, pointing out that currently the array only works convincingly when detecting explosives in a solution. It is less effective at picking out vapors of explosives from a person’s skin or belongings, he says, noting that the array works best when TNT vapor-containing air samples are blown directly at the nanowires.
Harvard University chemistry professor Charles Lieber says that the nanowire sensor approach is much more sensitive than the ICx polymer technology, which was developed in Swager’s lab, but it has not yet been proven the way the ICx technology has. Lieber, who focuses on biomedical applications of nanowire transistors, says the Israeli research shows that nanowire sensing could be applied for explosives detection and could be readily commercialized. “There are no limitations to the methodology from my perspective…it has potential to revolutionize explosives detection.”
Patolsky and colleagues are now making larger nanowire arrays coated with different molecules for detecting other kinds of explosives.