Research And Application Of Digital Microfluidic Devices With Integrated Microchannel Plate

Traditional microfluidic devices are based on microchannels and microvalves,etc.,which deal with continuous fluids and are prone to channel blockage and cross-contamination.The accuracy and precision are also limited.Digital microfluidics is a technique to operate discrete fluids,which can independently and precisely identify and manipulate samples in the microliter to nanoliter volumes,thus enabling parallel and large-scale analysis and detection.There are currently two main types of digital microfluidic chips,droplets and microchambers.The droplet chip is mainly based on electrowetting technology,which requires the design of complex circuits and the external connection of power supply.The throughput of the system is limited by the number of electrodes.As for microchamber array chips,the core microporous components usual y require complex microfabrication processes,including tedious lithography and etching steps.The number of reaction chambers is affected by the preparation process and the detection throughput is limited.Therefore,it is of great importance to develop an integrated digital microfluidic chips to perform high performance bioassays and analysis.Microchannel plate（MCP）,which contains high-porosity micrometer capillary arrays,can be mass-manufactured with fiber draw process without cumbersome fabrication procedures.In this thesis,it is firstly introduced and integrated as a key component in microfluidics to achieve high performance digital immunoassays.The porosity of MCP is 1.6×10⁵ units/cm² which leads to a detection range of up to 5 orders of magnitude.digital direct fluorescence immunoassay for Ig G and enzyme immunoassay assays for BβG are successfully achieved on this device.Meanwhile,using the oblique angle deposition technique,gold nanopillars are integrated on the sidewalls of the MCP to realize the amplification of fluorescence due to local surface plasmon resonance（SPR）.This metal nanostructure can experimentally achieve a fluorescence enhancement factor at least 2 orders of magnitude higher than the glass substrate,greatly improving the sensitivity of immunofluorescence detection.This device has the promise to be widely used for highly sensitive large-scale biomarkers.Further,MCP owns the advantage of homogeneous and large porosity and can be monolithically integrated into microfluidic chips for high-throughput emulsions.The throughput of the conventional step emulsion device ranges from about 50 to 300 L m^-2 h^-1 with a coefficient of variation from 5%to 20%.By optimizing key parameters including the viscosity relationship between the two phases and the flow rate of the dispersed phase,the droplet generation throughput of our MCP emulsion device can reach up to 500 to 700 L m^-2 h^-1 and the coefficient of variation is around 4%,which is among the best of reported microchannel emulsification device.Finally,the device was demonstrated for the preparation of high-throughput homogeneous gel microspheres and cell culture experiments.1.5×10⁶ microspheres were prepared in 1 min with an average size of 41μm and a variation coefficient of 7%,showing good monodispersity.The rough surface of the microspheres enabled seeding cell in a density of 8.08×10⁷cels/ml.After 24 h of incubation,the cell attachment rate to the microspheres was calculated to be 112±7%.Cells were cultured for a total of three days.The viability of the cells was detected to increase exponentially with the number of days of culture using the CCK-8 kit.The cels were stained with a live-dead staining kit,and the survival rates of the cells were all above 96%.In summary,MCP is introduced into digital microfluidic devices,which can not only achieve high-performance digital immunoassays,but also be applied to high-throughput,monodisperse droplet generation and gel microsphere preparation.The device is expected to be widely used in cell culture,biomolecular analysis and other fields for rapid and accurate digital microfluidic assays.