Caged-Fluorescence Imaging

Like traditional dye injection techniques, the caged-fluorescence technique allows optical extraction of information about scalar transport in microfluidic systems. A caged-dye is homogeneously distributed throughout a buffer solution and then injected into a microfluidic system. To obtain concentration information, the buffer was excited to fluoresce through two independent laser excitation events: 1) an uncaging of the dye and 2) an application of fluorescence exciting illumination. A time sequence of independent realizations is then obtained and processed. The caged-fluorescence method is especially useful in flow field interrogation, as the technique essentially allows for an “optical injection” of a well-defined sample plug. This eliminates any initial sample distortion that would be created through the physical injection of dye by hydrodynamic and electrokinetic means.

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