Micro‐computed tomography for the investigation of stationary liquid–liquid and liquid–gas interfaces in capillaries

Abstract

For better understanding and optimization of multiphase flow in miniaturized devices, micro-computed tomography (μCT) is a promising visualization tool, as it is nondestructive, three-dimensional, and offers a high spatial resolution. Today, computed tomography (CT) is a standard imaging technique. However, using CT in microfluidics is still challenging, since X-ray related artifacts, low phase contrast, and limited spatial resolution complicate the exact localization of interfaces. We apply μCT for the characterization of stationary interfaces in thin capillaries. The entire workflow for imaging stationary interfaces in capillaries, from image acquisition to the analysis of interfaces, is presented. Special emphasis is given to an in-house developed segmentation routine. For demonstration purposes, contact angles of water, liquid polydimethylsiloxane, and air in FEP, glass, and PMMA are determined and the influence of gravity on interface formation is discussed. This work comprises the first steps for a systematic 3D investigation of multiphase flows in capillaries using μCT.

A general design procedure for gas–liquid Taylor flow T-junction microreactors

“…[1][2][3][4][5][6] There have been a lot of reports on the gas-liquid two-phase microflow, as one of the most important research directions of microchemical technology. [7][8][9][10][11][12][13][14][15] Browsing these reports, we can find that the T-junction microchannel has been used and researched most frequently due to its simple structure and easy scale up. 16,17 Triplett et al systematically studied the airwater flow in a microtube, and proposed the flow map for the gas-liquid microflow based on the superficial flow velocity of the two phases.…”

3D investigations of microscale mixing in helically coiled capillaries

“…In this perspective paper, Xray micro-computed tomography (X-µCT) is applied to visualize 3D concentration profiles of iodide (I − ) in an HCT. X-µCT is non-invasive and offers high spatial resolutions without requiring optical access [30,31]. Even though X-ray based computed tomography has already been successfully applied for the characterization of processes on a larger scale, among others [32][33][34][35][36][37], studies concerning its extension to the mini-or microscale are limited [31] and only very few studies concern the X-ray based investigation of mass transfer related problems [38][39][40].…”

Micro‐computed tomography for the 3D time‐resolved investigation of monodisperse droplet generation in a co‐flow setup

“…X-ray based μ-CT is a noninvasive measurement technique allowing high spatial resolutions (<10 μm) and overcoming the challenges related to optical imaging. 44 Despite the wide use of tomographic imaging in the fields of chemical engineering and process engineering, [45][46][47][48][49][50][51] the extension to mini-and microfluidics is an innovative approach. 44 One major challenge in (Table 2).…”

“…In this work, we tie in with this research gap and apply X‐ray based micro‐computed tomography (μ‐CT) for the investigation of droplet formation in circular capillaries. X‐ray based μ‐CT is a noninvasive measurement technique allowing high spatial resolutions (<10 μm) and overcoming the challenges related to optical imaging 44 . Despite the wide use of tomographic imaging in the fields of chemical engineering and process engineering, 45‐51 the extension to mini‐ and microfluidics is an innovative approach 44 .…”

“…X‐ray based μ‐CT is a noninvasive measurement technique allowing high spatial resolutions (<10 μm) and overcoming the challenges related to optical imaging 44 . Despite the wide use of tomographic imaging in the fields of chemical engineering and process engineering, 45‐51 the extension to mini‐ and microfluidics is an innovative approach 44 . One major challenge in using X‐ray based tomographic imaging for dynamic processes in micro process engineering is the limited temporal resolution, which can range from a few minutes to several hours.…”