In liquid crystals, Homogeneous alignment sometimes called Planar alignment - this is the state of alignment of molecules which is opposite to homeotropic alignment

Homeotropic alignment

In liquid crystals, homeotropic alignment is one of the ways of alignment of liquid crystalline molecules. Homeotropic alignment is the state in which a rod-like liquid crystalline molecule aligns perpendicularly to the substrate. In the polydomain state, the parts also are called homeotropic domains...

. The molucules here align parallel to a substrate.

For planar alignment - polyimides can be used. One of the popular ones is PI-2555.

The surface has to be rubbed by paper or by a velvet or similar cloth in order to make the alignment axis parallel to the rubbing. However the exact mechanism if this alignment is not entirely clear.