Published online by Cambridge University Press: 05 September 2014
This study presents the fluid temperature measurement at a 90-degree sharp bend inside a microchannel using molecule-based temperature sensor technique. This technique provides both detailed and global information for temperature investigation in microfluidic research. Rhodamine B was selected as the molecule-based temperature probe in the experiment to provide non-invasive and straightforward measurements. To resolve the luminescence deviation in the microscale temperature measurements introduced by the corner structure, in-situ calibration method and pixel-by-pixel correction were applied during the data reduction. The temperature measurement was performed in a 200μm wide, 67μm deep and 2cm long PDMS microchannel with a 90-degree sharp bend at the center. The temperature profile was measured at a Reynolds number of 27.66 using Rhodamine B in DI water while the bottom of channel was heated at 50°C. As revealed by the molecule-based temperature sensor, the temperature variation along the central line increased 2°C while passing the corner. Additionally, the lateral temperature distributions upstream of the corner show the temperature increase near the outer side of microchannel and decreased near the inner side. The velocity profiles around the 90-degree sharp bend were acquired to analyze the flow after corner. Secondary flow structure after the corner was observed in the velocity profiles along the depth of the microchannel. This study analyzes the thermal flow fields in the microchannel with a 90-degree sharp bend and reveals that regardless of the low Reynolds number, the flow mixing after the corner resulted in the increase of temperature downstream of the bend.