In situ temperature sensing with fluorescent chitosan-coated PNIPAAm/alginate beads
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The interest in the development of non-contact temperature sensors for particle image velocimetry (PIV) is continuously growing. The integration of thermochromic tracers in PIV represents a critical step forward in experimental fluid mechanics, which would enable detailed full-field analysis of thermal and environmental flows. In this paper, interpenetrated polymer networks (IPN) PNIPAAm/alginate loaded with Nile Red (NR) fluorescent dye are used to develop beads for simultaneous non-contact temperature sensing and flow tracing in fluids. The novel IPN beads are coated with chitosan to properly modulate particle permeability in water. The thermochromic response of the fluorescent tracers is studied through fluorescence spectroscopy, evidencing an increase in the NR fluorescence emission up to twenty times above the lower critical solution temperature of PNIPAAm. These findings confirm the potential of fluorescent chitosan-coated PNIPAAm/alginate beads for in situ temperature in PIV.
This research was supported by the National Science Foundation through Grant No. CBET-1332204. The authors also acknowledge the support of the Office of Naval Research through Grant No. N00014-10-1-0988 that has allowed the acquisition of equipment used in this study. The first author acknowledges New York University for the hospitality during his visit in 2016 when this work was completed.
M.B. designed and performed the experiments and analyzed the data; F.C. and I.C. designed the experiments, analyzed the data, and wrote the first draft of the manuscript; S.D.P. and M.P. formulated the research questions; and all the authors revised the manuscript and participated in the discussion of the experiments.
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Conflict of interest
The authors declare that they have no conflict of interest.
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