Characterization of a Raman Spectroscopic and Holographic System for Gas‐Liquid Flows in Microchannels

Abstract

The description and prediction of the highly transient processes on the molecular scale in gas-liquid Taylor flows in microchannels are a great challenge. Due to a lack of in situ measurement techniques with satisfactory spatial and temporal resolution, existing models and numerical simulations of reactive two-phase flows are poorly developed. The Raman spectroscopic and holographic system presented herein overcomes shortcomings regarding the high temporal resolution and concomitant difficulties with the high energy densities that must be coupled into microstructured devices to give good limits of detection. It gives insight into the concentration profiles in the liquid phase within the microchannel to study the interaction between hydrodynamics, mass transport, and reaction kinetics.

Reaction Systems for Bubbly Flows

“…The combination of Raman and Mach‐Zehnder holography led to images of CO 2 bubbles in a millimetric channel setup (Figure ) . A rectangular channel with a cross‐section of 2 × 2 mm provided optical access to the Taylor flow.…”

“…Combined Raman spectroscopy and Mach‐Zehnder holography: distance between the measuring points (lowest point of bubble and laser spot) where the concentration was measured. Reproduced from ref …”

Method for Measuring the Three-Dimensional Morphology of Near-Wall Bubbles and Droplets Based on LED Digital Holography

“…22−24 Nevertheless, existing measurement techniques for gas−liquid interfaces still face challenges, including insufficient resolution, challenges in real-time measurements, and complex data analysis. 25,26 Hence, there is a need to explore high-precision, instantaneous, and quantitative methods for the three-dimensional morphology measurement of gas−liquid interfaces.…”

“…However, current observations of bubble transport in microfluidic chips mostly rely on two-dimensional imaging, and the three-dimensional morphology of the gas–liquid interface near the walls remains unmeasured. In addition, for the manipulation of droplets on solid surfaces, especially in precisely controlling droplets using biomimetic superwetting materials, understanding the three-dimensional surface morphology of droplets and the changes in the wetting behavior of solid surfaces is crucial. − Nevertheless, existing measurement techniques for gas–liquid interfaces still face challenges, including insufficient resolution, challenges in real-time measurements, and complex data analysis. , Hence, there is a need to explore high-precision, instantaneous, and quantitative methods for the three-dimensional morphology measurement of gas–liquid interfaces.…”