Researchers at North Carolina State University have developed a cheap and easy method for assembling nanowires by controlling their alignment and density.
Assembling
Alignment is a critical first step for developing devices that use nanowires because, usually during fabrication, small randomly oriented nanoscale wires ranging between 10 and 100 nanometers in diameter are obtained.
Controlling both alignment and the number of nanowires in a given area is commonly called "assembling" the nanowires. Before any practical applications can be pursued, the researcher must assemble the nanowires such that the nanowires align in a common direction in an orderly way giving the required density.
Method
In the new method, researchers deposited the nanowires on a stretched rubber substrate and then released the tension on the substrate. When the nanowires settled, they aligned at a right angle to where the tension was coming from.
The method is very similar to placing nanowires within a stretched rubber band and snapping it back to its original shape when the nanowires would be oriented in only one direction. The more the rubber substrate is stretched, the more aligned the nanowires will be and the greater the nanowire density will be.
Researchers claim that this method can also be used for nanowires synthesized by different methods or processed in different conditions. Researchers have demonstrated this claim using silver nanowires synthesized in solution and silicon nanowires synthesized by the vapor-liquid-solid method.
Applications
The researchers hope the findings will foster additional research into a range of device applications using nanowires, from nanoelectronics to nanosensors, especially on diverse unconventional substrates such as rubber, silicon, glass, plastic and paper. The use of a rubber substrate in this method facilitates broad research and manufacturing sectors such as stretchable nanoelectronics involving aligned nanowires on a stretchable rubber substrate. Similarly, rubber is also the material used as "stamps" in transfer printing in manufacturing nanodevices on various substrates. The researchers note that the initial step of the method, when the nanowires are first deposited on stretched rubber, sometimes yields an inconsistent degree of nanowire alignment. However, researchers feel that understanding the fundamental interface mechanics of adhesion and static friction between nanowires and rubber substrates is important to lead to a better control of the assembly process and hence a higher yield of the nanowire assembly.