In this work, we explore the surface interactions of liquid crystals (LCs) confined within carbon nanopipes (CNPs). CNPs differ from carbon nanotubes in the fact that they are very straight and open on both sides. Extensive research has been performed on CNPs to explore their potential as storage pipes for liquids. After demonstrating their wetting behavior and ability to transport aqueous and organic fluids, it was necessary to study the storage of complex fluids to understand the realm of fluids transportable by CNPs.

The CNPs used for this research had dimensions of, on average, 10 µm in length, 300 nm in diameter and a wall thickness of 15 nm; the LC used was 5CB, a well-characterized nematic LC. The LCs were imbibed by the CNPs by capillary action in their nematic state. Surface wetting studies of LCs on thin carbon films equivalent in structure and chemistry as the CNPs showed no contact angle, indicating perfect wetting. Polarizing optical microscopy was used to image the macroscopic LC orientation within the CNPs and to observe the alignment imparted to the bulk LC. Scanning electron microscopy (SEM) was used to observe the wetting characteristics of LC within the CNPs. In addition to these observations, data indicating the partial/complete filling of open-ended tubes will be presented.

Considering the intended applications of CNPs for microfluidics, it is vital to probe for techniques that align tubes and pipes in a fluid medium. The ordering of the LC molecules in the nematic range influences the ordering of the CNPs. CNP ordering can be observed in different layer depths of the LC. However, this is also accompanied by the sedimentation of pipes on the substrate. This leads to a converse effect of enhancing the order parameter of the LCs. Using Polarizing optical microscopy, well-aligned LC domains have been observed on ordinary glass microslides. Also, we investigated the effects of an electric field on the LC textures and the CNP positions. The application of electric fields leads to rotation of LC molecules, which exert torques on CNPs. At a threshold voltage, the CNPs rotated out-of-plane, which was observed as defects in the LC textures. The effects of electric fields at different frequencies, magnitude and shape on CNT manipulation will be discussed. Also, the influence of CNP concentration on LC textures will be presented.