Surface chemistry in polymer microfluidic systems

Abstract

This chapter explains the properties of polymers that are critical to their application in microfluidics. These properties include hydrophobicity, electroosmotic flow mobility, surface charged groups, and nonspecific adsorption. When choosing a polymer material for use in microfluidic systems, it is important to consider both fabrication issues as well as application needs. For fabrication, properties of the bulk polymer related to its machinability are important which include glass transition melt temperature, crystallinity, and UV absorption. Polymer microchannel surface chemistry can be defined by two fundamental parameters that are critical for their application in microfluidics: the total surface charge density, and the types of surface-bound chemical moieties. Fabrication of microchannel involves the use of thermoplastics, thermosets, and elastomers. In thermoplastics, plastic can be subjected to thermo-mechanical treatment at high temperatures and reformed into new stable structures. In thermosets and elastomers the shape remains stable upon heating up to the point of decomposition. With thermosets there is a high degree of crosslinking, while with elastomers there is a low degree of crosslinking making these materials soft and deformable. It is anticipated that the use of polymer substrates in microfluidic systems can progress rapidly as the surface chemistry of various polymers and stable methods for surface modification of polymer microchannels become available.