Thermoplastics are highly attractive substrate materials for microfluidic systems, with important benefits in the development of low cost disposable devices for a host of bioanalytical applications. While significant research activity has been directed towards the formation of microfluidic components in a wide range of thermoplastics, sealing of these components is required for the formation of enclosed microchannels and other microfluidic elements, and thus bonding remains a critical step in any thermoplastic microfabrication process. Unlike silicon and glass, the diverse material properties of thermoplastics opens the door to an extensive array of substrate bonding options, together with a set of unique challenges which must be addressed to achieve optimal sealing results. In this paper we review the range of techniques developed for sealing thermoplastic microfluidics and discuss a number of practical issues surrounding these various bonding methods.
