The alignment behaviors of two different types of MWCNTs, CNT A and CNT B, under the application of DC electric field were studied. CNT A had diameter and length ranging between 10–20 nm and 10–15 μm, whereas CNT B was much longer and thinner than CNT A, with diameter and length ranging between and between 60–80 nm and 7–10 μm, respectively. They had essentially the same surface treatments before experiments. Fig. 2 presents the alignment behaviors of CNTs of different contents in acetone as the dispersion medium before and after the application of electric field.