Integration of functionality into polymer-based microfluidic devices produced by high-volume micro-moulding techniques

Microfluidic devices with integrated functional elements have gained increasing attention in recent years. Many prototypes covering a wide range of applications have been fabricated and tested, especially in the fields of chemical and biomedical sciences. Nevertheless, integrated microfluidic devices are still far from being widely used as cost-efficient commercial products, often because they are produced by fabrication methods that are not suitable for mass production. Several methods have been recently introduced for cost-efficient high-volume production of micro-featured plastic parts, such as microinjection moulding and hot embossing. These methods have been widely used for fabricating simple disposable microfluidic chips on a commercial scale, but have not yet been similarly applied for producing integrated microfluidic devices. This review paper aims at presenting the state of the art in integrated microfluidic devices produced by cost-efficient high-volume replication processes. It takes microinjection moulding and hot embossing as its two process examples. Several types of elements are classified according to their functions, defined relative to their physical inputs and outputs. Their level of integration is reviewed. In addition, elements are discussed from a manufacturing viewpoint in terms of being readily produced by replication techniques or by back-end processes. Current and future challenges in integration are presented and discussed.