High throughput laser-induced fluorescence droplet micro-thermometry

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 tem-perature is evaluated throughout a cooling of the microfluidic chip, allowing the study of heat exchanges at the droplet microscale. (c) 2023 Elsevier Ltd. All rights reserved.

Automated summary

This paper evaluates a new high throughput temperature measurement method at the micro-scale. The method is non-invasive and utilizes laser-induced fluorescence of highly monodisperse dye-doped microdroplets in microfluidic channels. Real-time temperature sensing is achieved using two thermo-responsive dyes and a single excitation with a 532 nm laser. The ratio of fluorescence intensities from the two dyes shows a-1.4% variation per degree, indicating the method's versatility for different microchannel sizes. The method is also used to evaluate the thermal evolution of microdroplets' inner temperature during cooling, enabling the study of heat exchanges at the microscale.