The technique of Fluorescence Lifetime Imaging Microscopy (FLIM) has beenudemployed to quantitatively and spatially map the fluid composition and temperatureudwithin microfluidic systems.udA molecular probe with a solvent-sensitive fluorescence lifetime has beenudexploited to investigate and map the diffusional mixing of fluid streams underudlaminar flow conditions within a microfluidic device. Using FLIM, the fluidudcomposition is mapped with high quantification and spatial resolution to assess theudextent of mixing. This technique was extended to quantitatively evaluate the mixingudefficiency of a range of commercial microfluidic mixers employing various mixingudstrategies, including the use of obstacles fabricated within the channels.udA fluorescently labelled polymer has been investigated as a new probe forudmapping temperature within microfluidic devices using FLIM. Time CorrelatedudSingle Photon Counting (TCSPC) measurements showed that the averageudfluorescence lifetime displayed by an aqueous solution of the polymer dependedudstrongly on temperature, increasing from 3 ns to 13.5 ns between 23 and 38 oC. Thisudeffect was exploited using FLIM to provide high spatial resolution temperatureudmapping with sub-degree temperature resolution within microfluidic devices.udA temperature-sensitive, water-soluble derivative of the rhodamine Budfluorophore, effective over a wide dynamic temperature range (25 to 91 oC) has beenudused to map the temperature distribution during the mixing of fluid streams ofuddifferent temperatures within a microchannel. In addition, this probe was employedudto quantify the fluid temperature in a prototype microfluidic system for DNAudamplification.udFLIM has been demonstrated to provide a superior approach to the imagingudwithin microfluidic systems over other commonly used techniques, such asudfluorescence intensity and colourimetric imaging.
展开▼
