A dc electric field was applied to a dispersion containing 0.1 wt.% of VGCFs® in silicone oil in two directions, perpendicular and parallel to the observation direction, as illustrated in Fig. 2. In situ optical microscope observation allowed detailed characterization of the resulting aligned structure of VGCFs®. Fig. 4 shows a series of optical micrographs as a function of time for the two directions. Before application of the dc electric field, the axial directions of the fibers were randomly oriented (Fig. 4(a) and (b) at 0 min). It was difficult to experimentally determine the average fiber–fiber distance. However, the average distance was estimated to be around 6 μm between the centers of fibers, assuming that 0.1 wt.% of the dispersed VGCFs® (average length of 4 μm) was located at the corners of the cubic model.