Microfluidic gas-flow profiling using remote-detection NMR.

We have used nuclear magnetic resonance (NMR) to obtain spatially and temporally resolved profiles of gas flow in microfluidic devices. Remote detection of the NMR signal both overcomes the sensitivity limitation of NMR and enables time-of-flight measurement in addition to spatially resolved imaging. Thus, detailed insight is gained into the effects of flow, diffusion, and mixing in specific geometries. The ability for noninvasive measurement of microfluidic flow, without the introduction of foreign tracer particles, is unique to this approach and is important for the design and operation of microfluidic devices. Although here we demonstrate an application to gas flow, extension to liquids, which have higher density, is implicit.