In computer magnetic disk devices, the magnetic head floats in the air with a slight gap above the disk surface. The gap height in the data writing section is less than a few nanometers, and gas molecules flow at a very close distance to the magnetic disk or magnetic head. Therefore, it is considered that van der Waals forces, which are intermolecular forces from the wall surfaces, act on gas molecules near the wall surfaces. Especially when the gap size is small, the internal gas flow may be significantly influenced by the attractive force from the wall surfaces.
YAMANE et al. (Wed,) studied this question.