Development of injection moulded, ultrasonically welded immiscible phase filtration devices

Having advanced tremendously over the past two decades, microfluidics is today a well-established scientific field. The governing physics are under control and the teething troubles of preliminary device fabrication have been overcome. The applications of microfluidics are wide ranging from components in inkjet printing, to disposable chips for point-of-care diagnostics, to advanced chemical analysis systems. Nevertheless, the original prophesied commercial success as a whole has been limited.
The modest existence of microfluidic devices as products is due in part to a manufacturing schism that has befallen the field. In academia,microfluidic devices have historically been fabricated using materials and technologies that while efficient at rapid prototyping, are near incompatible with industrial mass production. The research conducted has generated immense knowledge of such techniques and materials, however, technology transfer to the industry is challenging.
This PhD project has focused on applying industry-compliable technologies for rapid prototyping of microfluidic devices. In specific, a thermoplastic disposable microfluidic chip system for sample preparation has been realised. The device appliesmagnetic bead-based solid-phase extraction for nucleic acid extraction from biological samples, using the immiscible phase filtration (IPF) approach. Device development has employed injection moulding for part fabrication and ultrasonic welding for bonding. Rapid prototyping was accomplished by micromilling and laser micromachining of mould inserts, allowing for design-to-production of chips within a day. The rapid overall fabrication cycle of a few minutes per chip allowed for conducting research in a single-use disposable fashion.
Chip development has centred on manufacturing of an IPF chip, by generating a microfluidic channel system capable of fluid handling using capillary forces. A key aspect of IPF is to replace the required washing steps of the magnetic beads with passage through capillary microvalves. Furthermore, much development has gone into creating energy directors for ultrasonic welding, suitable for microfluidic systems. A methodology has been established where energy directors can be quickly added to existing mould inserts, using laser micromachining. The produced device was performance tested by isolating methicillin-resistant Staphylococcus aureus from bovine whole blood, followed by off-chip quantification using real time quantitative polymerase chain reaction.