Fig. 4

a Four representative categories of the SWCNTs alignment. b Phase map of alignment tendency with varying widths of the hydrophilic region (\( {\text{W}}_{{{\text{SiO}}_{2} }} \)) for a given concentration (~0.1 mg/ml). As shown, the degree of alignment was decreased with increasing the hydrophilic region (from case 1 to case 4)