Disclination in nematic liquid crystal as superelastic rods

Unlike elastic materials, the energies of disclinations in nematic liquid crystal are correlated linearly to their length. Here, based on the Landau-de Gennes phenomenological method, we investigate the elastic behaviour of disclinations confined by two patterned surfaces. By translating and rotating one of the surfaces, the disclinations were stretched and twisted, respectively. Thus, the elastic properties of disclinations can be measured, including line tension, torsional rigidity, shear modulus and effective bending stiffness. The energy of disclinations is determined by their length and the difference in the phase angle of the two surfaces. We observed the bending of stretched disclinations, under twist, from simulations and experimental results validated this coupling behaviour. Under a critical twist angle, the deflections of curved disclinations increases linearly with the twist angle and translate distance. We present a toy model that explains the bend-twist coupling of disclinations, which contains the fourth mechanical parameter, bend-twist coupling g. The bend-twist coupling of disclinations is favoured by the twist distortions of the nematic liquid crystals. These new findings help predicting the dynamic behaviour of disclinations and manipulate the disclinations more intuitively.