Figure 22.

(a) The sketches show the orientation of CNC in sequential sections of a chiral nematic helicoid with axis normal to the plane of the page. (In other words, the orientations shown side by side should be envisaged as being one behind the other, with the sketch on the left being at the front.) The CNC concentration is assumed high enough for gel formation, and the free surface is at the top of the sketches. On evaporation (b) the tendency of the CNC gel to shrink to a greater extent parallel to the CNC orientation may lead to a surface ripple with a periodicity of P/2 along the chiral nematic axis.