Production of microfluidic chips from polydimethylsiloxane with a milled channeled surface for modeling oil recovery during porous rock waterflooding

Abstract

Microfluidic chips with porous structures are used to study the flow of oil-containing emulsion in the rock. Such chips can be made from polydimethylsiloxane by casting into a master mold. At the initial stages of research, fast and cheap prototyping of a large number of different master molds is often required. It is proposed to use milling to make a channeled surface on a polymethyl methacrylate plate, from which a negative image should be taken, which is the master mold for casting positive polydimethylsiloxane chips in it. Several epoxy compositions have been tested to make this master mold. The main requirement in the search for the material was the exact replication of the geometry and sufficiently low adhesion to polymethyl methacrylate and polydimethylsiloxane for removing the product with minimal damage to the mold. It was possible to make master molds from all the materials used, but with defects and various degrees of damage. One of the epoxy compositions was found suitable for making a master mold with many elements simulating the grains of a porous medium (height to width ratio 2:3). The developed method makes it possible to use polydimethylsiloxane for prototyping chips simulating the porous structure of an oil rock.

Plasma Surface Modification of PDMS-Glass Microfluidic Chips for Oil Recovery Studies

“…It is known that in nature the wettability of natural rocks dominated by silicates is primarily determined by primary extraction [27]: if most nano-and micropores are filled with water, then the surface will be hydrophilic; if the pores are filled with non-polar liquids, then such a surface will be hydrophobic. Polydimethylsiloxane (PDMS), from which chips are made for modeling flows in rocks [28], is a porous material with a contact angle of about 120 • . With this initial contact angle, the primary water extraction does not lead to an increase in hydrophilicity, since water does not enter the pores of the PDMS.…”