These observations are in line with the expectation of formation of a preferential CNT network in the field direction [29]. In addition, individual nanotube alignment can lead to an increase in conductivity when slight alignment occurs but can also cause a disruption of the conductive network at high alignment levels [39]. The phenomenon in the perpendicular to the alignment direction is weaker [39] as a result of the combination of the formation of more conductive paths and their disruption of the network in this direction. The time scales of the phenomenon reported in Fig. 4 imply a dominance of the preferential aggregation process rather than individual CNT alignment, whilst the results of microscopy (Fig. 5) are suggestive of occurrence of some individual alignment mainly in the high field case (45 A/m2). It can be inferred that the conductivity increase is governed by preferential aggregation with the existence of aligned nanotubes playing a minor role in electrical response.