SADDLE-SPLAY ELASTICITY IN NEMATIC LIQUID-CRYSTALS

The effect of the saddle-splay elastic constant K-24 on nematic direct or-fields is a topic of fundamental interest for the elastic theory of liquid crystals and plays a vital role in device applications where n ematic liquid crystals are confined to a curved geometry. The first me asurement of K-24 came more than sixty years after the pioneering work of Oseen, who made first steps toward the elastic theory of liquid cr ystals. Today the study of saddle-splay elasticity has become an impor tant topic in liquid crystal physics. In this review we summarize the various methods used to measure K-24 in curved geometries and present the detailed theory behind the measurements.