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Open Access Publications from the University of California

Measuring concentration fields in microfluidic channels in situ with a Fabry-Perot interferometer

  • Author(s): Vogus, DR
  • Mansard, V
  • Rapp, MV
  • Squires, TM
  • et al.

© The Royal Society of Chemistry 2015. Recent advancements in microfluidic technology have allowed for the generation and control of complex chemical gradients; however, few general techniques can measure these spatio-temporal concentration profiles without fluorescent labeling. Here we describe a Fabry-Perot interferometric technique, capable of measuring concentration profiles in situ, without any chemical label, by tracking Fringes of Equal Chromatic Order (FECO). The technique has a sensitivity of 10-5RIU, which can be used to track local solute changes of ∼0.05% (w/w). The technique is spatially resolved (1 μm) and easily measures evolving concentration fields with ∼20 Hz rate. Here, we demonstrate by measuring the binary diffusion coefficients of various solutes and solvents (and their concentration-dependence) in both free solution and in polyethylene glycol diacrylate (PEG-DA) hydrogels.

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