Review of Microfluidic Devices and Imaging Techniques for Fluid Flow Study in Porous Geomaterials

Abstract

Understanding transport phenomena and governing mechanisms of different physical and chemical processes in porous media has been a critical research area for decades. Correlating fluid flow behaviour at the micro-scale with macro-scale parameters, such as relative permeability and capillary pressure, is key to understanding the processes governing subsurface systems, and this in turn allows us to improve the accuracy of modelling and simulations of transport phenomena at a large scale. Over the last two decades, there have been significant developments in our understanding of pore-scale processes and modelling of complex underground systems. Microfluidic devices (micromodels) and imaging techniques, as facilitators to link experimental observations to simulation, have greatly contributed to these achievements. Although several reviews exist covering separately advances in one of these two areas, we present here a detailed review integrating recent advances and applications in both micromodels and imaging techniques. This includes a comprehensive analysis of critical aspects of fabrication techniques of micromodels, and the most recent advances such as embedding fibre optic sensors in micromodels for research applications. To complete the analysis of visualization techniques, we have thoroughly reviewed the most applicable imaging techniques in the area of geoscience and geo-energy. Moreover, the integration of microfluidic devices and imaging techniques was highlighted as appropriate. In this review, we focus particularly on four prominent yet very wide application areas, namely “fluid flow in porous media”, “flow in heterogeneous rocks and fractures”, “reactive transport, solute and colloid transport”, and finally “porous media characterization”. In summary, this review provides an in-depth analysis of micromodels and imaging techniques that can help to guide future research in the in-situ visualization of fluid flow in porous media.

The Impact of Wettability on Dynamic Fluid Connectivity and Flow Transport Kinetics in Porous Media

“…Many researchers have sought to gain insight into micro‐scale fluid displacement phenomena through micromodel experiments (Hu et al., 2017b ; Jahanbakhsh et al., 2020 ; Kim et al., 2012 ; Park et al., 2017 ; Zhang et al., 2011 ; Zheng & Jang, 2019 ) and/or numerical simulations (Azizi et al., 2019 ; Cao et al., 2016 ; Ferrari et al., 2015 ; Hu et al., 2017a ; Ryazanov et al., 2014 ; Wu et al., 2016 ; B. Zhao et al., 2019 ).…”

Radiotherapy on-chip: microfluidics for translational radiation oncology

“…Indeed, most studies investigating radiopharmaceutical compounds on-chip developed microfluidic microreactors or quality-control devices, mainly for positron emission tomography (PET) radiotracers. [105][106][107][108][109][110][111][112][113][114] For example, Taggart et al engineered a microfluidic platform for radiation detection, and used it to quantify the activity of PET tracers 2-[18F] fluoro-2-deoxy-D-glucose and [68Ga] gallium-citrate as well as single photon emission computed tomography (SPECT) radiotracer [99mTc] pertechnetate (Fig. 2E).…”

Manufacturing of Microfluidic Devices with Interchangeable Commercial Fiber Optic Sensors

“…At a distance of 12.5 mm from the inlet and the outlet The microfluidic device tested has a uniform pore network pattern (15.58 mm long and 8.00 mm wide) that represents a 'generic' porous test structure. Such, and similar, patterns are often used as benchmarks to investigate flow, transport, and reactive processes in porous media [17][18][19][20]. The pattern consists of circular pillars with a diameter of 0.4 mm, which are evenly spaced from each other by 0.5 mm, creating a uniform network of microchannels with 0.1 mm wide throats (see Figure 1c).…”

“…In hydrology, microfluidic chips are used to test water quality, including the detection of waterborne pathogens (e.g., E. coli bacteria) and inorganic pollutants (e.g., heavy metals) [11]. In petroleum engineering and CO 2 storage research, they are often used as physical models of porous media to study different phenomena related to flow, transport, and reactive processes on the microscale (pore level), e.g., the displacement of immiscible fluid phases, fluid trapping and saturation, precipitation of minerals, and dissolution of solvents and chemical compounds [12][13][14][15][16][17][18][19][20].…”