What manufacturing challenge prevents carbon-nanotube bundles from reaching their predicted strength?

To reach their predicted theoretical tensile strength, carbon-nanotube bundles must be manufactured as long, perfectly ordered structures where all nanotubes share the same diameter and atomic arrangement.1

Currently, the primary challenge is that the technology to produce such long (more than one metre), uniform bundles does not exist, and there is no clear strategy for achieving this level of precision. In practice, materials fail to reach their "intrinsic strength" due to the propagation of microscopic defects; while a bundle of nanotubes could theoretically bypass this by preventing defects from propagating across the bundle, the inability to manufacture these perfectly ordered, large-scale assemblies prevents the material from realizing its full potential.1