Figure 4

Defect array imitated by external pressure waves and coupling between the pressure wave and director profile. (a) By pressing a cell with a sharp tweezer tip, an outward LC flow generated an anti-clockwise circular director profile (top). In contrast, upon releasing the cell, an inward LC flow produced a clockwise director arrangement (bottom). A 0.2 wt% R811 chiral dopant was added to the LC. (b) Pressing four points with sharp tweezer tips produced a similar pattern with the same +1 defect as that in Figure 1b. The bottom images, which were obtained from an oblique observation, exhibit the inversion of the handedness of the concentric director profiles of both the pressing points and the automatically generated defect point (center point). Red and green circular arrows denote the clockwise and anti-clockwise director arrangements. (c) Flow vector fields at the ‘pulse ON’ time (p₊ stage); the red and green solid circles denote the converging and diverging flow points (that is, the highest and lowest pressure points), respectively. The dotted lines are nodal lines.