By mixing an ionic impurity into a nematic liquid crystal, we recently found a system which enables large-scale self-organization of a two-dimentional square array of umbilical defects without requirement of pre-patterned surfaces. Here, we focus on the stabilization of the grid-like pattern in a local region by a photo-polymerization method. It is found that the boundary of the cured region helps smoothly connect the non-polymerized defects induced by an electric field.
