Generation And Manipulation Of Gelatin Microdroplets In Microfluidic Device With Through-hole-on-wall Of Crossed Round Microchannels

Microfluidics is becoming more and more important as an interdisciplinary technique.Microfluidic chip droplets generation technology which plays an inportant role in biological miniaturization experiment, becomea the rapid dvelopment direction recent years. In this thesis, based on polydimethylsiloxane (PDMS) microfilament molding method, through-hole-on-wall of crossed round microchannels device are used to generate gelatin micro-droplets.First, we report a microfilament molding method to build through-hole-on-wall of crossed round microchannels device, and integrate microfilament molding method, we discuss the possibility to produce a new microfluidic device of configuration microstructurethe on polymethyl methacrylate methyl ester (PMMA) substrate. Then, based-on crossed microchannel, we constructed a T-type through-hole-on-wall of crossed round microchannel through blocking one side of the cross-hole.Secondly, the conditions micro-droplets generated through controlling gas / liquid two-phase and liquid / liquid two-phase in the above device are consided, focusing on the gelatin droplets on condition of liquid / liquid two-phase. The results show that the required minimum flow ratio of dispersed phase to continuous phase has relation to the type of oil phase, the channel diameter and the concentration of gelatin solution.①When the microchannel diameter is 150μm and the dispersed phase of gelatin solution concentration is 2%, the minimum flow ratio of the silicone oil and edible oil is 75 and 15 respectively.②When edible oil is continuous phase and gelatin solution of 2% concentration is dispersed phase, gelatin droplets genration require the minimum flow ratio is 15, 22.5, 27.5, 36.5, 51 in the microchannel with the diameter of 150μm, 100μm, 80μm, 60μm, 40μm.③When the diameter of the microchannel is 150μm and made the edible oil as the continuous phase, the gelatin solution has the concentration of 1%, 2%, 3%, 4%, 5%, the corresponding minimum flow ratio will be 12.5, 15, 20, 31.5, 41. Through a series of tests, we get the best conditions of gelatin droplet generation, when channel diameter is 150μm, gelatin concentration is 2%(w/v%)and edlble pil made as continue phase, gelatin droplets with 140μm diameter can obtain steadily of six in a minute at the flow ratio of disperse phase reached 32μl/min. At the same time, the gelatin droplet is spherical, named gelatin microspheres. Furthermore, gelatin microspheres were generated in cross-over round microchannels. Thirdly, we compared the defference between T-channel and cross channel in generating gelatin micro-droplets, the pressure in T-type channels being required is smaller, and the gelatin export is single, so that the ratio of the flow needed is smaller, The minimum flow ratio of gelatin droplets formed the former is 9, but the latter is 15. also the frequency of gelatin droplets generated were 36 and 2 in one minute. In addition, we gennerate and manipulate gelatin micro-droplets in our new and improved PDMS / PMMA micro-channels.Finally, based on the recognization of droplets genrated in the above microchannel device, we make a further discuss on the possibility of manipulation droplets fixed on the cross-hole downstream the microchannel. The generated droplets are fixed and collected in defferent methods, making use of the special structure of through-hole-on-wall of crossed round microchannels and the biochemical characteristics of gelatin solution. Gelatin or agar solution become solid at temperature below the freezing point, the pressure of nitrogen and the flow of continuous phase will push the generated droplets to cross-hole surface, and then the entire chip device colled at 4℃in refrigerator, gelatin or agar droplets are fixed at the cross-hole due to the freezing cold. Layout the filaments before channel formed, dip little oil on the filaments surface, then pore-structure attached to microchannels are made out. When the droplets generated from the cross-hole upstream flow to the pore, they are"retained"and fixed here. The application of the gelatin droplets we also do the first exploration in some degree, and manipulate the gelatin droplets to package cells successfully, also single cell was isolated. Then the cell culture in microchannels was made a superficial solution.