Quantitative measurement of depth–averaged concentration fields in microchannels by means of a fluorescence intensity method

We have inferred and verified an optical measuring technique, based on fluorescence intensity, for the species concentration field in a liquid microchannel flow. In contrast to macroscopic flows, where a light sheet is usually applied, the complete illumination of the measuring volume in the microchannel provides a heightaveraged concentration field. The technique was verified with aqueous solutions within a square glass microchannel of 110 lm width. The verification experiments confirm both a good spatial resolution and a good accuracy of even the concentration gradients within a concentration boundary layer.