# Perspectives in Liquid-Crystal-Aided Nanotechnology and Nanoscience
## 4 LC-Aided-Assembly and Self-Assembly of Nanomaterials
At the same time, such carbon nanotube liquid crystals (CNTLCs) can also be formed with the assistance of external forces such as magnetic field [345], electric field [331], and especially shear [346]. Nevertheless, suspending CNTs at a high concentration in a solvent is not always straightforward. CNTs are notoriously difficult to disperse in any medium and the long-term stability of the dispersion is poor because of the strong attraction from van der Waals forces between CNTs. To obtain a homogeneous suspension of CNTs, various chemical approaches have been employed [347; 348; 349; 350; 351]. In addition, CNTLCs usually show numerous topological defects that do not coarsen with time due to their length and waviness [352; 353], as well as the high viscosity (Figure 14a-d). This is unfavourable for the optimum performance of CNTs and thus seriously hinders their applications. Methods such as mechanical shearing [354], as well as changing the morphology of CNTs [355], have been applied to obtain homogeneously aligned CNTLCs. CNTs are excellent conductors and have exceptional conductivity anisotropy. The electrical conductivity along the main axis of the tube can typically be several orders of magnitude larger than that in the tube's radial direction. As a consequence, with the assistance of self-assembly CNTLCs, CNT films with specific structures, vertically aligned CNT arrays or horizontally aligned CNT arrays, can be obtained, which will have considerable potential to be used as transparent electrodes [356; 357; 358; 359]. Compared to the traditional ITO electrodes, which are suffering from difficulties such as the brittleness of ITO, the rising cost of indium, and the high vacuum and temperature processing during the production, CNT electrodes have great advantages in terms of their flexibility, low cost, safe fabrication process and special conductivity anisotropy, which make them a good substitute for ITO in the LCD industries [360; 361]. CNT films can also act as alignment layers to orient LC molecules via the CNT substrates due to the orientational structure and the \(\pi\)-\(\pi\) interaction between them [362; 363; 364; 212] (Figure 14e,f). Apart from that, CNTs also show anisotropic optical responses due to the anisotropy and the graphite \(\pi\) electrons. When the polarization of the incident light is perpendicular to the tube axis, there will be no attenuation; in contrast, if they are parallel to each other, there will be strong absorption. Such anisotropic absorption not only exists in the visible region, but also in ultraviolet and infrared regions. This optical property produces a highly aligned CNT film to be used in various optical applications [365; 366; 367] (Figure 14i,j). Last but not least, CNTLCs can also be used to fabricate continuous and multifilament fibres. These lightweight fibres show a uniform morphology with few defects and a high degree of CNT alignment (Figure 14g,h). They have excellent mechanical, electrical and thermal properties and can be applied in the field of smart and strong materials including smart textiles, conductive composites and electric wires [368; 369; 370]. Furthermore, since GO has an extremely large aspect ratio, it is expected that aqueous GO dispersions can also self-assemble into lyotropic LCs according to [PERSON]'s theory (Figure 15a,b). Although there have been a fair number of studies focused on the liquid crystallinity of aqueous GO dispersions, it should be noticed that the first relevant study for graphene LCs was that of [PERSON] et al., who dispersed graphene in chlorosulfonic acid [163]. One should recall that graphene is hardly soluble in water and organic solvents, which severely limits its application in LCs. Instead, GO has long been known to disperse well in water due to its tunable amphiphilic properties. In 2011, [PERSON] et al. first reported the liquid crystallinity of GO [164]. The liquid crystalline properties of GO dispersions have since been studied intensively.