Scientists have developed an inexpensive technique called "microcombing" that can be used to align carbon nanotubes (CNTs), which could lead to the production of ultra-strong and pure CNT films.
This breakthrough could be used to improve electrical conductivity of these films, which could lead to applications in electronics and aerospace, North Carolina State University reported.
"It's a simple process and can create a lightweight CNT film, or 'bucky paper,' that is a meter wide and twice as strong as previous such films -- it's even stronger than CNT fibers," said Yuntian Zhu, Distinguished Professor of Materials Science and Engineering at NC State.
The researchers started off by growing CNTs on a conventional substrate in closely packed array; the CNTs were entangled in a way that caused them to form a "ribbon" if they were pulled from either end of the array. This ribbon was attached to a spool that allowed it to be neatly wound up.
As the spool pulls, the ribbon is dragged between a pair of fissured surgical blades that create microscopic fissures on their cutting surface. The fissured create a "microcomb" that aligns the CNTs in a similar fashion to a comb being pulled through tangled hair.
As the aligned CNTs are being wound onto the spool, an alcohol solution is applied to pull them even closer together to form a super strong bond. The CNT ribbon is layered on top of itself as the spool winds it up, creating the pure CNT film.
This new technique allows the researchers to control the film's thickness by regulating the number of layers, and the result boasts twice the tensile strength and 80 percent higher electrical conductivity than an uncombed CNT film.
"This is a significant advance, but we want to find ways to make CNT alignment even straighter, it's still not perfect," Zhu said. "In addition, the technique would theoretically be easy to scale up for large-scale production. We'd like to find an industry partner to help us scale this up and create a material for the marketplace."
The findings were published in a recent edition of Science Daily.
