Effect of surface roughness on bond strength between PCTE membranes and PDMS towards microfluidic applications

Abstract

Microfluidic platform is an enabling technology for a wide range of applications such as life science research, material synthesis, drug discovery and environmental monitoring and protection. Most applications require separation or filtration of samples such as cell or particle separation which can be achieved by manipulating flow and channel geometries, leveraging external forces or integrating on-chip membranes. Membranes are convenient without the need of precise control of flow and channel dimensions or the need to use external forces. Polydimethylsiloxane (PDMS) which is one of the most widely used materials for making microfluidic devices has also been used to make on-chip membranes, but the integration appears to be tedious and have low reproducibility. Polycarbonate track-etched (PCTE) membranes which can be manufactured to a high standard are excellent alternatives and have demonstrated success in microfluidic applications. However, their use in microfluidics has been limited due to the lack of details for their integration with microfluidic devices. This study provides an improved understanding of the bond strength between PCTE membranes and PDMS and presents a detailed set of procedures for bonding them by aminosilane-mediated plasma treatment. Due to the manufacturing process, the membranes have a smooth and rough side, which were carefully evaluated in terms of their bonding strength with PDMS devices for a range of applied pressures. It was found that the smooth side should be preferentially chosen as the primary bonding surface, however, with proper procedures, the rough side can achieve similar results. Both procedures are provided in detail, which can have a significant impact on the performance of microfluidic devices that require a sandwiched membrane structure.