Application Of Microdroplets And Alginate Particles In Microfluidic Devices

Since MEMS (Micro Electronic Mechanical System) technique was born at the end of20th century, it has gained constantly progress in the past several decades. As a branch of MEMS,^TAS (micro total analysis systems) technology has received much attention from the scientists in the past20years. With MEMS technique, this new technology aims at integration and miniaturization of traditional analysis equipments into micro-chip at centimetre or millimetre scale, and finally realizes portable, individual and democratic analysis and diagnose. The process of design and production of the microfluidic chip involves physics, biology, chemistry, micro-electronics, machining and even clinical medicine.For the widely use of microfluidic chips in biology and clinical medicine, the integration of biocompatible materials in biological micro-channels could made them diversified and multifunctional. Alginate, as a naturally occurring polymer, has been widely used in food industry and medicine for its good biocompatible characteristic. Its applications in microfluidic chips are popular as well.The produce of microdroplets and microparticles was one of hot off the press of sample preparation in micro-channels. Manipulation of single droplet with biomaterials, could be used as microreactor for transportation, mixing, and analysis. Microparticles encapsulated with drugs or cells could be directly synthesized in microchips and put into use in areas such as biology and dignoses. In this dissertation, microfluidic chips were used to generate particles with different composition and function by microfluidic technique, and discussions about these properties of these particles were also given.The major work in this dissertation includes:1. According to the object and content of experiments, we designed and used microfluidic chips with different structure and function, which includes single-layer chip made from PDMS and glass slade, double-layer chip made from PDMS and glass channel layer, and double-layer chip with two layers of PDMS. We also integrated microelectrode and vent valve with microchips.2. We not only realized Cell immobilization by double-layer chip made from PDMS and glass channel layer, but also integrated generating calcium alginate capsule by flow-focusing method with fixing capsule in microfluidic chips. It is simpler than fixing cells directly, and cells are easier to observe under the protection of alginate gel.3. E.coli and bifid bacteria were chosen in our research. Gel dishes encapsulated with microorganisms were immobilized in microfluidic chips. Culture medium was renewed constantly with syringe pumps, and an incandescent was used to keep the temperature fit for the growth of microorganisms. We observed propagation of microorganisms by the microscope, and recorded it by a CCD camera. Feasibility and advantages of cell immobilization and culture by microcapsules in microfluidic chips was determined in this experiment.4. PDMS double-layers chips with vent valves were made, and were controlled by a Labview program. Micro-valve structure was formed in the microfluidic chips. On the basis of drop generation in T-shape chips, we studied the influence of pressure and driving times to the sizes of droplets, to regulate the volume of droplets in microchips. Droplets were manipulated by micro-valves, and active mixing was realized by regulation of speed of oil and driving times. In the last, mixing test of mercury ion and fluorescent probe confirmed the feasibility of mixing with the devices and its potential in environmental detection.5. Dished and rectangular gels were generated by flow-focusing method and template method, respectively. Different applications were carried out according to the generation methods.6. AuNPs were synthesized on alginate gel particles generated by template method in situ by chemical synthesis. Chloroauric acid was used as oxidant traditionally, while L-ascorbic acid was used as reducer. Generation was realized by green method without introducing toxic materials and complicated catalytic condition to it. By regulating the diffusion time of reactants in the alginate gels, anisotropic gel particles were generated with single layer containing AuNPs. Soon after, we characterized this feature by SEM and XPS analysis.