Nanotube Fiber Fabrication Goes Organic

Carbon nanotubes (CNTs) often get a bad rap for clumping in aqueous solutions, but researchers put a positive spin on this property about a decade ago. By first dispersing the CNTs in sulfuric acid and then streaming them through a spinnerette into water, scientists forced the nanostructures to condense into macroscopic fibers. Manufacturers have since developed this technique to create high-strength, low-weight conductive fibers as alternatives for more massive metallic cables, but commercial spinning processes still rely on harsh acids. Researchers at Rice University led by Angel A. Martí and Matteo Pasquali have now developed an acid-free method that disperses a matrix of nanotubes and potassium ions in a blend of dimethyl sulfoxide and crown ethers (ACS Nano 2014, DOI:10.1021/nn502552q). Nanotubes are negatively charged in the organic solvent, causing them to repel one another. But potassium cations trapped in crown ethers partially block this repulsion, allowing the team to create highly concentrated suspensions of well-aligned nanotubes. Using these suspensions, the team can spin fibers with mechanical and electrical properties on par with their acid-forged counterparts.