| Micro-fluidic chip is based on the research on the control of fluid flow in micro-nano size space.It is a new branch of microfluidics in recent years,and is widely used in chemical,biological,military and other fields.With the maturity of chip fabrication technology,many processes,such as injection molding,molding and thermoforming,have been developed.However,due to the limitation of fabrication technology and means,the micro-channel is mostly of rectangular section,It is difficult to process small scale,and the cost of processing is expensive and so on.The methods are active and passive ways used for the generation of micro-droplets,including the T-junction channel method,the pneumatic method,and so on.At present,the research of similar methods is mainly built in the microchannel of rectangular cross section,its controllability,fluid fluidity,and high throughput need to be improved.In this paper,a fabrication technology of sandwich glass T-junction chip is presented,which is made of glass circular cross-section microchannel and PDMS substrate and upper cover based on hot deformation principle.The formation mechanism of droplet in the chip is also studied.The method changes the traditional processing technology,and has the advantages of simple processing,low cost,and good fluid fluidity.The droplet size is also reduced and the droplet flux is increased.The main work is as follows:1.Analysis of the common effects of the dimensionless parameters,micro channel droplet dynamics in wettability,contact angle and Marangoni effect on droplet formation,to establish the relationship between the main parameters,which lays the theoretical foundation for the simulation model in the analysis of the influence of droplet size factors.2.Based on the basic theory of two-phase flow,a numerical model of droplet generation is established.Based on the T microchannel,the influence of wettability,interfacial tension,viscosity of continuous phase,continuous phase velocity and capillary number on the volume of droplet was simulated and analyzed.The controllability of droplets within the circular cross-section microchannels was verified.In addition,based on the area of equal section,the results of droplet generation between circular section and rectangular cross-section microchannel are compared reduce about 10μm,and the advantage of circular section microchannel chip is verified.The parameters are provided for the control of droplet size in the preparation of liquid droplets.3.The structure and preparation method of a sandwich type microchannel micro-fluidicchip with circular cross section are proposed.The structure of the chip mainly includes the floor layer,the channel layer and the cover plate layer,in which the channel layer is connected by the paraffin microsphere as a sacrificial material.To build an experimental platform for preparing drawing platform,capillary wax microspheres and preparation of the final chip,The diameter of the drawn capillary is controlled at 10-300μm.The experimental process and control parameters to analyze chip to complete the processing and analysis provide experimental platform foundation for droplet preparation experiment and results of follow-up.4.The homemade microfluidic chip(R1/R2=250/100μm)was used to prepare the droplet.With silicone oil,deionized water as a continuous phase and dispersed phase droplet preparation,hrough the use of different fluids,the change of continuous phase viscosity and velocity parameters are obtained for different droplet size.Its size changes exponentially or logarithmically with viscosity or flow rate,compared with the ideal simulation results,the error is less than 10μm.The relation verified by circular micro channel drops the controllability and stability generated with in circular cross-section microchannel and further shows the superiority of the proposed chip structure in this paper. |
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