Processes for integration of microfluidic based devices

Lab-on-a-chip and microfluidic device technology is in the early stages of commercialization. A major market is medical point-of-care (POC) and other kinds of portable diagnostics. Such systems require assembly and fluidic interconnection among the microfluidic elements and other components. However, microfluidic chips have until now been produced in relatively small numbers. While the structuring methods to make the fluidic channels are based on well established micro-manufacturing techniques such as lithography and embossing and are in general suited to mass manufacture, packaging and assembly methods require development for larger manufacturing volumes. One problem is with reliable sealing of a capping layer to the microfluidic layer for large area polymer wafers. In conventional thermocompression bonding the high pressures and need to heat the whole thickness of the polymer stack leads to potential distortion of the microfluidic structures. We present results on trials on the use of low frequency induction heating to deliver heat directly to the bonding interface thus permitting the use of lower bond pressures. The selection and structuring of susceptor materials is reported, together with analysis of the dimensions of the heat affected zone. Acrylic plates have been joined using a thin (<10 mum) nickel susceptor providing a fluid seal that withstood a fluid pressure of 590 kPa. Another problem is how to provide support structures for connection of capillary tubing or for directly connecting microfluidic chips together to form systems. We propose the use of polymer overmoulding to create a meso-scale fluidic manifold, with anticipated advantages for manufacturing of ease of assembly and low part count. Results on the reliability of the fluid seal achieved by direct adhesion between overmould materials and glass are presented. A demonstrator overmoulded structure to connect a glass microfluidic chip to capillary tubing, using a compliant grommet for sealing, is also reported.