Liquid infiltration into carbon nanotube fibers: effect on structure and electrical properties

Carbon nanotube (CNT) fibers consist of a network of highly oriented carbon nanotube bundles. This paper explores the ingress of liquids into the contiguous internal pores between the bundles using measurements of contact angles and changes in fiber dimensions. The resultant effects on the internal structure of the fiber have been examined by WAXS and SAXS. A series of time-resolved experiments measured the influence of the structural changes on the electrical resistivity of the fiber. All organic liquids tested rapidly wicked into the fiber to fill its internal void structure. The local regions in which the nanotube bundles are aggregated to give a bundle network were broken up by the liquid ingress. For the range of organic penetrants examined, the strength of the effects on structure and electrical resistivity was correlated, not only with the degree to which the liquid reduced the nanotube surface energy, but also with the Hansen affinity parameters. The fact that liquid environments influence the electrical performance of these fibers is of significance if they are to replace copper as power and signal conductors, with added implications regarding the possible ingress of external insulating materials, and possibly also sensing applications.