National Institute of Standards and Technology (NIST) and university researchers report a significant step towards solving the nanotube "problem", the challenge of overcoming processing obstacles so that nanotubes can be used in new polymer composite materials. According to the research team, their analysis reveals that during mixing, carbon nanotubes that are suspended in viscous fluids sort themselves by length. While this information isn't a "magic bullet", it is a step in the right direction.