Hi All, I am using rhodamine 6g mixed in a tiny bit of alcohol, which is then dissolved in DI water. I pass this dye solution into a micochannel( the microchannel cross section dimensions are 2.5mm x 100 microns)by means of a syringe pump. I have used both a xenon bulb and nd:yag laser as the light source. What I find is that the when the flow rate is faster, the intensity of the dye image is higher and it is lower when i decrease the flow rate. I find this strange as it is the same dye solution that i am using at both flow rates and the channel is completely filled with dye solution. Could any one of you explain what might be going on and how to overcome this? Also, if you could recommend a better dye, that would be great too. Thanks a bunch.. Vishwa