(a) The temperature in the interrogation area of the device as a function of distance from the edge of the cold channel, with the cold and hot channels at 12 and 50 °C, respectively. Dots are experimental measurements; solid line is a FEMLAB numerical simulation with no fitting parameters. (b) Concentration of fluorescein (in relative units) in the interrogation channels as a function of channel number with 0, 25, and 50 ppm solution of fluorescein fed to the 0, 50, and 100% inlet, respectively. A concentration of 1 corresponds to a 50 ppm solution.