Local fluorescence in micro channels for particle counting

We produce local fluorescence in polydimethylxiloxane (PDMS) microchannels with a low power laser. This technique can be used to count either particles or cells in microflows. A CCD webcam is mounted on the objective of a microscope to visualize the flow. Particles obstruct the fluorescence as they pass by, allowing for a simple counting method that is software controlled. We present the experimental setup and preliminary results.