title: Measuring concentration fields in microfluidic channels in situ with a Fabry-Perot interferometer.
abstract: 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(-5) RIU, 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.
authors: Department of Chemical Engineering University of California, Santa Barbara, USA. squires@engineering.ucsb.edu.
authors: Douglas R
authors: DR
authors: Vogus
authors: Vincent
authors: V
authors: Mansard
authors: Michael V
authors: MV
authors: Rapp
authors: Todd M
authors: TM
authors: Squires