In Situ Quantitative Measurement of Concentration Profiles in a Microreactor with Submicron Resolution Using Multiplex CARS Microscopy

Abstract

In situ quantitative imaging of concentration profiles of reactants and products inside a microfluidic reactor is achieved, with submicron spatial resolution with mM sensitivity and on ms time scales, for a given position. The label-free approach relies on quantitative vibrational spectroscopy, using Coherent Anti-Stokes Raman scattering microscopy in a spectrally resolved fashion, and is demonstrated on an elementary acid-base reaction.

Invited Review Article: Imaging techniques for harmonic and multiphoton absorption fluorescence microscopy

“…In situ quantitative imaging of product formation inside a microfluidic was demonstrated using CARS microscopy by Schafer et al 216 Spectra collected during the proton transfer reaction between acetic acid and pyrrolidine were decomposed into contributions from reactants and product with submicron spatial resolution, with ϳmM sensitivity and on a millisecond time scale. Label-free detection of the size distribution of mouse adipocyte cells was demonstrated by Wang et al also using CARS microscopy.…”

Coherent anti-Stokes Raman scattering microscopy for quantitative characterization of mixing and flow in microfluidics

“…Building on this success, microfluidic devices with integrated Raman microscopy have shown they can monitor thermal and chemical gradients, product formation, and conformational changes [4][5][6][7][8][9]. Within such devices, optical resolution of molecular kinetics is limited more by the optical sectioning than by the stability of the conditions within the microfluidic device.…”

“…In these applications, coherent anti-Stokes Raman scattering (CARS), a nonlinear Raman microscopy, is a particularly attractive alternative by virtue of its improved spatial and temporal resolution. We have previously demonstrated in situ quantitative CARS imaging of product formation inside a microfluidic device with submicrometer lateral resolution and ϳmillimolar sensitivity on a millisecond time scale [9]. Here, we use high-resolution mass transport measurements in microfluidic devices using CARS to infer the local flow profile, providing the necessary device characterization for subsequent studies on concentration-or time-dependent molecular dynamics.…”

Mikrofluidik in der anorganischen Chemie

“…Eine On-line-Integration der analytischen Methoden in das mikrochemische System würde eine bessere Optimierung ermöglichen und Zugang zu den kinetischen Parametern der chemischen Reaktion geben. Die Integration und Weiterentwicklung von analytischen Methoden wie Elektrophorese, [66] NMR-Spektroskopie, [143][144][145] Massenspektrometrie, [146] FTIR-, [147] IR- [148] und Raman-Spektroskopie [149][150][151] zur Untersuchung der Kinetik organischer Reaktionen wurden beschrieben. In der anorganischen Materialchemie hingegen scheint die UV/Vis-Spektroskopie die einzige In-situ-Methode zu sein.…”