Abstract
AbstractMicrofluidic sample manipulation is a key enabler in modern chemical biology research. Both discrete droplet‐based digital microfluidic (DMF) assays and continuous flow in‐channel assays are well established, each featuring unique advantages from the viewpoint of automation and parallelization. However, there are marked differences in the applicable microfabrication materials and methods, which limit the interfacing of DMF sample preparation with in‐channel separation systems, such as the gold standard microchip electrophoresis. Simultaneously, there is an increasing demand for low‐cost and user‐friendly manufacturing techniques to foster the adaptation of microfluidic technology in routine laboratory analyses. This work demonstrates integration of DMF with in‐channel separation systems using only low‐cost and accessible (non‐cleanroom) manufacturing techniques, i.e., inkjet printing of silver for patterning of the driving electrodes and UV curing of off‐stoichiometric thiol–ene (OSTE) polymers both for dielectric coating of the electrode arrays and replica molding of the microchannel network. As a dielectric, OSTE performs similar to Parylene C (a gold standard dielectric in electrowetting), whereas its tunable surface and bulk properties facilitate straightforward bonding of the microchannel with the dielectric layer. In addition, a new chip design that facilitates efficient droplet transfer from the DMF part to the microchannel inlet solely by electrowetting is showcased.
Highlights
Such as rinsing, preconcentration, reaction, assays and continuous flow in-channel assays are well established, each featuring unique advantages from the viewpoint of automation and parallelization
With respect to performance characterization, we addressed three critical aspects of successful digital-to-channel microfluidic integration, including the use and characterization of off-stoichiometric thiol–enes (OSTE) as new dielectrics for Digital microfluidics (DMF), droplet transfer from DMF to the microchannel inlet, and leakage-free bonding of the microchannel layer to the dielectric layer
The electrode arrays for both DMF and MCE were fabricated by inkjet printing of silver nanoparticles on a commercial mesoporous and flexible substrate (Novele IJ-220), which has been shown to provide a robust platform for manufacturing of low-cost DMF devices.[12]
Summary
With a view to mass manufacturing of DMF devices, benchtop inkjet printers provide a cost-efficient approach to rapid prototyping and design optimization of DMF devices using microfabrication materials that are considerably well transferable to high-throughput manufacturing processes (e.g., roll-to-roll printing). The electrode arrays for both DMF and MCE were fabricated by inkjet printing of silver nanoparticles on a commercial mesoporous and flexible substrate (Novele IJ-220), which has been shown to provide a robust platform for manufacturing of low-cost DMF devices.[12] In previous studies[25,27] involving hybrid devices that feature DMF sample preparation upstream of MCE separations, external platinum electrodes were required to be manually inserted into the inlets and outlets of the MCE chip These previous methods are suitable for prototypes but are not scalable for mass manufacturing. Much of the time went to MCE channel fabrication, which can be parallelized with the DMF (top and bottom plate) fabrication, and to one-by-one spin-coating of the inkjet-printed devices, which is easy to scale-up by adapting, for instance, roll-to-roll polymer coating techniques to the chip fabrication
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