2018 Volume 22 Issue 1 Pages 13-17
Optical manipulation of nanosheet liquid crystals prepared by exfoliation of inorganic layered crystals realizes local and on-demand orientation control of nanosheets. Although a tightly focused laser beam by using an objective lens with a high numerical aperture (NA) is typically employed for the optical manipulation to enhance the gradient force of an irradiated laser beam, the dominant driving force of the optical orientational manipulation of nanosheets has recently been attributed to the scattering force, suggesting that an objective lens with a high NA is not indispensible for the nanosheet manipulation. In this study, we carried out optical orientational manipulation of nanosheets using an objective lens with low NA, 0.4, and compared the results with those obtained by a lens with high NA, 1.2. Orientational manipulation was realized with both of the lenses, and the size of the manipulated domain using a lens with NA=0.4 was smaller than that obtained by using a lens with NA=1.2. The domain size increased with the irradiated laser power, reflecting the dominant contribution of scattering force to the optical manipulation of nanosheet liquid crystals.
