Quantitative Spatial Mapping of Mixing and Temperature in Microfluidic Systems
E.M. Graham, S.W. Magennis, K.G. Macnamara, D.P. Towers and A.C. Jones
University of Edinburgh, UK
microfluidic, mixing, temperature, FLIM, fluorescence
We have demonstrated that fluorescence lifetime imaging microscopy (FLIM) is a sensitive and highly quantitative method for spatially mapping fluid mixing in microchannels. This technique involves imaging the solvent-dependent fluorescence lifetime of a molecular probe, rather than the intensity, to directly report the spatial variation of fluid composition. This method is free from the problems that hamper conventional intensity-based optical techniques. The composition of the fluid can be simply and directly correlated to the fluorescent lifetime of the fluorophore. We can resolve changes of fluid composition as small as 2% in sub-picolitre interrogation volumes. FLIM images collected for the mixing of a molecular probe in solutions of methanol and a methanol/water mixture in a mixing flow cell show the spatial dependence of the molecular probe lifetime upon the composition of the fluid and can be used to visualise and map fluid mixing and composition in microchannels.
The application of FLIM has been extended to monitor the temperature changes and distribution within microchannels and heating chambers for microfluidic devices. In this case we are imaging the temperature-dependent fluorescence lifetime of a different molecular probe which can be used as a temperature distribution map.
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Nanotech 2006 Conference Program Abstract