Functionalisation of Polydimethylsiloxane (PDMS)- Microfluidic Devices coated with Rock Minerals

Abstract

Fluid flow in porous rocks is commonly capillary driven and thus, dependent on the surface characteristics of rock grains and in particular the connectivity of corners and crevices in which fluids reside. Traditional microfluidic fabrication techniques do not provide a connected pathway of crevices that are essential to mimic multiphase flow in rocks. Here, geo-material microfluidic devices with connected pathways of corners and crevices were created by functionalising Polydimethylsiloxane (PDMS) with rock minerals. A novel fabrication process that provides attachment of rock minerals onto PDMS was demonstrated. The geo-material microfluidic devices were compared to carbonate and sandstone rocks by using energy dispersive X-ray spectroscopy, scanning electron microscopy (SEM), contact angle measurements, and a surface profilometer. Based on SEM coupled with energy-dispersive X-ray spectrometry (SEM-EDS) analyses, roughness measurements, contact angle, wettability, and roughness were comparable to real rocks. In addition, semivariograms showed that mineral deposition across the different geo-material devices was nearly isotropic. Lastly, important multiphase flow phenomena, such as snap-off and corner flow mechanisms, equivalent to those occurring in reservoir rocks have been visualised. The presented approach can be used to visualise rock-fluid interactions that are relevant to subsurface engineering applications, such as hydrocarbon recovery and CO2 sequestration.

Microfluidics for Porous Systems: Fabrication, Microscopy and Applications

“…Other than glass functionalization, work has been done to functionalize PDMS microfluidics devices (Alzahid et al 2018;Zhang et al 2018). Zhang et al (2018) introduce the concept of layer-by-layer (LbL) coating of PDMS microfluidics devices.…”

“…This cycle is repeated 2-3 times to get the desired minerals thickness. Alzahid et al (2018) developed another approach to functionalizing PDMS and used two different rock minerals to obtain sandstone and carbonate microfluidic devices. Their method involved plasma treating PDMS, followed by injection of minerals solution, and the PDMS containing the minerals was then dried, cleaned and subjected to another plasma treatment to bond it to the PDMS cover.…”

Optical measurements of oil release from calcite packed beds in microfluidic channels

“…Other studies focused more on an adequate representation of the chemistry of the rock surface. Alzahid et al (2018) developed a method to coat sandstone and carbonate minerals on a poly(dimethylsiloxane) (PDMS) surface. They could visualize multi-phase flow phenomena such as snap-off (Roof 1970) and corner flow (Mohanty et al 1987) that usually occur in reservoir rock.…”

Maskless, rapid manufacturing of glass microfluidic devices using a picosecond pulsed laser

“…rock samples) for the investigation of different fluid flow phenomena that govern surface and subsurface systems. Thanks to these devices, it is possible to observe and study different multiphase fluid flow mechanisms that occur for instance between rock grains, such as snap-off and corner flow phenomena which are responsible for disconnection and trapping of carbon dioxide and/or hydrocarbons 26 .…”

“…poly-methyl-methacrylate (PMMA), polycarbonate (PC), cyclic-olefin-copolymer (COC)), renewable polymers (e.g. polylactic acid (PLA)), chromatography paper, photoresist, hydrogels, glass and silicon 26–35 . Depending on the material used, a microfluidic pattern can be generated by using soft lithography, casting, hot embossing, injection moulding, wax printing, inkjet printing, mechanical milling, laser micro-machining, two-photon polymerisation, etching or even 3D printing 36–42 .…”