Investigation On Microfluidic Preparation And Application Of Double Emulsion Droplets

Double emulsion droplet has the advantages of closed system,uniform size,designable internal junction and stability,showing great application potential in drug delivery and transportation,cosmetics industry,biomedicine and other fields.With the expansion of the application field of double emulsion droplet,the size and morphology of the related application field are increasingly strict.For example,water-oil-water mononuclear droplet can be used to prepare polymer microspheres for ICF targets.Due to the special internal and external structure,multi-nucleus double emulsion droplets are used for drug delivery and preparation of multifunctional microparticles.However,in multiphase flow system,droplet size,wall thickness,number of encapsulated droplets and formation process are significantly affected by many factors,which usually lead to droplet instability,diameter and monodispersity difficult to control.In addition,in inertial confinement fusion target with microspheres in the study,in spite of the microspheres preparation and thermal degradation have made certain achievements,but with the ICF high standards on spindle microspheres have a certain gap,especially the analysis of the affecting factors in preparation process optimization into a ball and thermal degradation of performance improvement still needs further research.In this paper,water-oil-water double emulsion droplets were prepared by droplet microfluidic technology and applied to ICF polymer microspheres,which are divided into the following three parts:（1）The effect of flow velocity on the morphology and structure of multi-core double emulsion droplets: Using two-step coaxial flow decline flow control device to carry out the regulation of droplet size shape First study the phase velocity influence on dual droplet diameter size,again according to the fluid flow between the droplet size and mass conservation,droplet number inside control of double droplets;On this basis,the droplet morphology was further regulated,and the flow pattern diagram of the droplet morphology with regard to the three-phase flow velocity was obtained.Finally,the accurate preparation of diversified dual droplet morphology was realized.（2）Research on size regulation and formation process of single core double emulsion droplets: On the basis of the above section,the specific formation process and size control of one single core double droplet were studied.A one-step coaxial microfluidic generator was used to study the effects of flow velocity and viscosity on the formation process and particle size change of double droplet.Firstly,the operating conditions for stable generation of single-core double droplet were optimized,and the formation process of double droplet was recorded by high-speed camera.The formation process was quantitatively distinguished according to the change of droplet morphology,and the force analysis and influencing factors were analyzed.Finally,according to the mass conservation relationship between fluid flow rate and droplet volume,the predicted droplet size is obtained and compared with the experimental value.（3）The application of double emulsion droplets in the preparation of microspheres: PAMS double emulsion droplets containing different concentrations of initiator were prepared by droplet microfluidic technology.After solidification,PAMS hollow microspheres were obtained.The surface sphericity and wall thickness uniformity of the microspheres were characterized by Keynce and X-ray,and experimental results were verified by theoretical simulation.Finally,the degradation properties were characterized by thermogravimetric analyzer.Based on the above research,this paper firstly discussed the variation of droplet number and droplet morphology with three phases flow rate in the size of double emulsion droplets,and successfully prepared the diversified double emulsion droplet morphology.On this basis,the formation process and size regulation rule of one kind of double emulsion droplets are studied,and the influence of flow velocity and viscosity on the size change and formation process of double emulsion droplets are discussed.Finally the water-oil-water droplet is applied to the double ICF polymer microspheres,in the analysis of the affecting factors into a ball of thermal degradation of performance etc.Carried on the thorough research The research for the construction of water-oil-water double emulsion droplets formation process,the preparation of polymer microspheres process research provides the experimental basis and theoretical guidance,to enrich and develop microfluidic technology Polymer microspheres and other disciplines are of great significance.