Double-Interface Behavior Characteristics Of Doubleemulsion Droplets In Micro-Channel

A microfluidic chip integrates the basic operating units of biochemical laboratories,such as sample preparation,reaction,separation,detection,cell culture into several square centimeters.As one kind of microfluidic,droplet-based microfluidic is more suitable for high-throughput analysis,less sample consumption and faster reaction time than continuous microfluidic.As one type of droplet,the double-emulsion droplet has good encapsulation and release properties of active substances.Therefore,it has been widely used in many fields such as drug discovery,cell research,and material synthesis.The double-interface behavior of double-emulsion droplets will affect the function and application of double-emulsion droplets.At present,the research on the dynamic of double-emulsion droplets was mainly focused on the deformation and less focused on the cases with interface restructure.Therefore,this paper will carry out the numerical study on the double-interface behavior with interface restructure in three aspects,which provides interface theory for the application of double-emulsion droplets.Firstly,the characteristics of interfacial behavior induced by inner droplet coalescence was studied.Then the effects of double-emulsion droplet size,viscosity and density of oil phase on the behavior of double interface were investigated.It is found that the deformation of the inner interface is transferred to the outer interface through the middle phase,which is resulting in the deformation of the outer interface.At the same time,the deformation of the inner interface is also bound by the outer interface.When the size of the inner droplet increases,the binding of the outer surface to the inner interface gradually increases.The interaction between the inner and outer surfaces increases so that the deformation of the inner interface first increases and then decreases.And the deformation of the outer surface increases.The deformation amount of outer interface changes from 0.015 to 0.126.When the size of inner and outer droplets increase at the same time,the binding of the outer surface to the inner surface gradually weakens resulting in the increase of the inner surface deformation and the decrease of the outer surface deformation.The deformation amount of outer interface changes from 0.098 to 0.082.When the viscosity of oil phase increases,the deformation of inner interface decreases.With the interaction between inner and outer interfaces increasing,the deformation of outer interface increases.The deformation amount of outer interface changes from 0.029 to 0.066.When the density of oil phase increases,the deformation of inner interface increases and the deformation of outer interface decreases.The deformation amount of outer interface changes from 0.048 to0.039.Secondly,the effect of inner interface on the reconstruction of outer interface was studied by the two-step-method of coaxial flow.The effects of inner droplet size,inner phase viscosity and the interfacial tension of inner interface on the reconstruction of outer interface were investigated.The study found that two types of double-emulsion droplets with the small core or the large core alternately appeared in the process of forming double-emulsion droplets.With the increase of droplet size,inner phase viscosity and the interfacial tension of inner interface,the sizes of the two types of double-emulsion droplets all showed an increasing trend.The size of two types of double-emulsion droplets changes from 325.88 ?m to 330.29 ?m and from 326.66?m to 331.1 ?m,respectively.Thirdly,the characteristics of interfacial behavior induced by inner droplet release were studied.Then the effects of inner droplet size,outer droplet size and fixed size ratio on interfacial behavior were discussed.It is found that there are four types of inner droplet release.That is Release in one time,Release in two times at left side,Partial release and Release in two times at right side.With the increase of the interfacial tension,the release type of the inner droplet changes from Release in one time to Release in two times at right side,which reflects the transition from low degree to high degree.When the size of the inner droplet increases,the release type of the inner droplet changes from low degree to high degree.The time of the inner droplet first release changes from 0.052 ms to 0.284 ms.When the size of the outer droplet increases,the release type of the inner droplet tends from high degree to low degree.The time of the inner droplet first release changes from 0.095 ms to 0.2 ms.With the increase of both inner and outer droplet size,the release type of inner droplet changes from low degree to high degree.The time of the inner droplet first release changes from 0.085 ms to 0.445 ms.With Di / Do changing to 1 and Oh number changing to 0,the release type gradually changes from low degree to high degree.