Separation of two-phase emulsions in a microchannel using wettability differences

Abstract Microchannels are widely used in various biomedical devices and microfluidic applications. Traditionally, the fabrication of microchannels has been a difficult task using conventional manufacturing technologies. However, using PMMA can simplify the process of creating microchannels without requiring a chemical process. In this study, researchers investigated the separation of water and oil in microfluidic chips in a laboratory setting. First, a microchannel was designed and made of PMMA by laser engraving. To bond the chips together, they were placed in an oven. Then, using a syringe pump, liquids were injected into the microchannels at flow rates of 0.25, 0.38, and 0.5 mL/min, with a maximum flow rate of 1.6 mL/min. The separation efficiency was then calculated. The results showed that the separation efficiency in the hydrophilic and hydrophobic channels at a flow rate of 0.25 mL/min was better than that at a flow rate of 1.6 mL/min. In the hydrophilic channel, the maximum separation efficiency was 0.92, and the minimum separation efficiency was 0.34. In the hydrophobic channel, the maximum separation efficiency was 0.92, and the minimum separation efficiency was 0.38. The results also showed that the separation efficiency decreased as the volumetric flow rate increased. At low volumetric flow rates, capillary forces are stronger and more important than other forces, resulting in better separation in terms of hydrophilicity and hydrophobicity.