Capillary flow traversing a backward facing step (BFS) in a microchannel at low Capillary
and Weber numbers is investigated in detail using analytical, numerical and experimental
techniques. The BFS's under study included both open surface, where a free surface is
formed at the top to the channel, and closed surface, where a lid with a different contact
angle than the base material is used. An analytical model valid for both geometries was
derived to determine the capillary pressure as a function of the liquid-gas interface position …