Frey O, Misun PM, Fluri DA, Hengstler JG, Hierlemann A.

Nat Commun. 2014 Jun 30;5:4250. doi: 10.1038/ncomms5250

Reconfigurable microfluidic hanging drop network for multi-tissue interaction and analysis.

“Maximal flow velocities appear at the liquid–air interface”. Uses open capillary channels and valves.