High throughput laser-induced fluorescence droplet micro-thermometry

AUTHORS

• Guérin Gautier
• El Abed Abdel

KEYWORDS

Droplet microfluidics Laser induced fluorescence Thermal measurements Lab-On-Chip

Document type

Journal articles

Résumé

This paper assesses a new temperature measurement method at the micro-scale at high throughput. This non-invasive method is based on laser-induced fluorescence of highly monodisperse dye-doped flowing microdroplets in microfluidic channels. Laser-Induced-Fluorescence (LIF) of two thermo-responsive dyes (Rhodamine B and rhodamine 110) enables temperature sensing in real-time at high acquisition rates. A single excitation with a 532 nm laser shows satisfying fluorescent emission with no absorption overlap. The emission signals from both dyes are analyzed, and the ratio of both fluorescence intensities shows a-1.4% variation per degree, similar to our observations with dissolved dyes in a single phase microfluidic flow. The ratiometric computational method gives similar results for two droplet sizes, underlining the method's versatility for various microchannel sizes. The thermal evolution of microdroplets' inner temperature is evaluated throughout a cooling of the microfluidic chip, allowing the study of heat exchanges at the droplet microscale.

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