The recent development of microfluidic systems like µ-TAS and µ-heat excha...

Abstract: The feasibility of employing laser-induced fluorescence (LIF) techniques to study thermal transport at the microscale is investigated. Two implementations of fluorescent thermometry are considered: a two-dye system and a single-dye, two-color system. In the two-dye implementation, a highly temperature-sensitive fluorescent dye (Rhodamine B) and a second dye (Sulforhodamine-101) with a different (weaker) temperature sensitivity are used in tandem to determine fluid temperature with high accuracy and low noise utilizing a pulsed Nd:YAG laser as an illumination source. While the fluorescence intensity of the temperature-sensitive dye is proportional to temperature, it is also biased by variations in the illuminating intensity. Therefore, the second dye with a different temperature sensitivity is required to compensate for such biases. Calibration of this two-dye LIF implementation reveals a temperature sensitivity of –1.5%/K and –2.7%/K when dissolved in ethanol and water, respectively, with volumetric illumination from a Nd:YAG laser. The feasibility of this methodology for conducting temperature measurements is explored by assessing the steady-state, linear temperature profile generated across a microfluidic channel array with two large hot and cold reservoirs. These measurements reveal that the mean steady-state temperatures in the microchannels are within ±0.4oC of the predicted temperatures with experimental uncertainties (based on standard deviation) of ±0.48–0.59oC (relative uncertainties of 1.4–2.0%