Magnetic resonance velocimetry reveals secondary flow in falling films at the microscale

To design better falling film microreactors, concrete knowledge of the flow and the ability to produce complex channel structures are
necessary. The efficiency of falling film microreactors is most often determined by studying the composition of the liquid after it has exited
the system. In the present study, Magnetic Resonance Velocimetry is used to obtain three-dimensional, three-component velocity fields inside
of falling films flowing in open microchannels. The microchannels were made by two-photon polymerization. It was possible to resolve the
complex shape of the liquid–gas interface and to observe, for the first time, secondary flow inside of a falling film at the microscale.