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

Abstract

Wetting hysteresis is the most important characteristic of microfluidic chips for modeling multiphase flows in rocks, including for oil production problems. Plasma modification of surface wetting characteristics is well studied, but there is a problem of stabilizing the resulting surface for use in a liquid hydrocarbon media. In this work, a simple and accessible technology for modifying the surface of PDMS and glass using a dielectric barrier discharge in a chamber based on the d’Arsonval apparatus has been developed. The surface wetting hysteresis for PDMS and glass was studied as a function of the plasma treatment time. It is shown that with the help of plasma treatment it is possible to change the wetting angles of the walls of microfluidic chips in a very wide range, thereby simulating the conditions of both hydrophobic and hydrophilic rocks. At the same time, PDMS has the widest possible range of changes in the wetting angle; the advancing contact angle decreases from 120° to 10°; receding contact angle—from 70° to 0° during plasma treatment. It has been shown that plasma treatment of a microfluidic chip, together with a 30 min primary extraction with oil and salt water, leads to a significant change in the wetting characteristics of its surface. This in total leads to an increase in the oil displacement efficiency from the chip by about 10%. In general, the results of the study showed that plasma surface treatment for the hydrophilization of microfluidic chips is a simple and affordable technology for controlling the wetting characteristics of microfluidic chips. PDMS in this case is a promising material.

Keywords

• laboratory-on-a-chip
• surface modification
• contact angle
• plasma
• primary extraction
• rock flooding