Microfluidic technology, refers to the science and technology of systems to manipulate small amounts of fluids with microchannels. It makes systems like "lab-on-a-chip (LOC) systems" possible and is being nominated as a game player in the chemical or life science area. Nevertheless, efficient and reliable packaging and interfacing strategy for microfluidic chips is still the challenge ahead for the continuing development and commercialization of microfluidics.

Due to the diversity of microfluidic types, various interconnect strategies specific to the target microfluidic applications have been developed. They can be categorized into permanent gluing and sealing connections and reversible and fixing interconnections. Permanent gluing and sealing connections represent advantages o...[ Read more ]

Microfluidic technology, refers to the science and technology of systems to manipulate small amounts of fluids with microchannels. It makes systems like "lab-on-a-chip (LOC) systems" possible and is being nominated as a game player in the chemical or life science area. Nevertheless, efficient and reliable packaging and interfacing strategy for microfluidic chips is still the challenge ahead for the continuing development and commercialization of microfluidics.

Due to the diversity of microfluidic types, various interconnect strategies specific to the target microfluidic applications have been developed. They can be categorized into permanent gluing and sealing connections and reversible and fixing interconnections. Permanent gluing and sealing connections represent advantages of easy fabrication, excellent non-leaking performance and low-cost but face with clogging issues or poor alignments and are challenging to repair and remove. Alternatively, reversible and fixing interconnections are adhesive-free, reusable but with cumbersome interfaces at times.

3D printing has been nominated as the promising manufacturing approach to provide more flexibilities and superiorities to the fabrication of microfluidic interconnections. However, current 3D printed connectors are still having issues with compatibility of existed microfluidic types or high-density integration. Various 3D printing approaches have been introduced and discussed, in which coaxial printing is ideal for hollow microfluidic connector fabrication.

In this study, UV-assisted coaxial 3D printing is implemented to provide a general interconnection solution for microfluidic devices. To fabricate hollow connectors with channels at a micro-scale, water serves as the sacrificial layer to avoid channel collapsing, and it can be drained out from the openings on the substrate during the printing. Simultaneously, UV-curable adhesives are utilized for shell formation with excellent adherence and compatibility for microfluidic substrates, based on in-situ UV curing mechanism.

To accomplish the printing process, a UV-assisted coaxial printing system has been developed with an assembled coaxial nozzle, a converged UV-LED light source and a 3D movement stage. Furthermore, material characterizations involving the FTIR spectrum, UV rheology and photo-DSC measurement are performed to study the UV curing behaviors of adhesives used in the study and thereby master the printing process. For the fabrication of printed connectors, processing criteria are discussed subsequently and parametric studies are performed for investigation, involving the process window, the influence of flow rates to the inner channel dimension and printing repeatability.

Besides, mechanical testing, including the pull test, shear test and pressure test is conducted to evaluate the mechanical strengths of fabricated connectors in this study, in which fabricated connectors represent mechanical robustness for their operations. Furthermore, test vehicles are manufactured to integrate the printed connectors to typical PDMS-Glass microfluidic devices, which successfully demonstrates the functionality and integration feasibility of directly printed connectors for microfluidic interconnections.