Research On Fabrication Of Guided Microcapsules And Controllable Release Of Their Encapsulants Based On Double-emulsion Droplets

As an effective carrier and vehicle,microcapsules have numerous applications in a wide range of fields including drug delivery,food processing,environmental protection and so on.Droplet microfluidic technology has emerged as a powerful method for the fabrication of microcapsules because of their advantages of high encapsulation efficiency,flexible operation and excellent size-controllability.Double-emulsion droplets with unique core-shell structure are widely used as templates for the microfluidic fabrication of microcapsules.A critical requirement for the microcapsules toward practical application is the precise guidance and controllable release.To date,most studies achieve the guiding movement of microcapsules by adding specific response substances directly,but this may cause some tissues such as incompatibility and cross-contamination.Therefore,in this paper,we present a novel guided microcapsule structure and controlled release method based on droplet microfluidics and electrohydrodynamic theory.Firstly,the mechanism of droplets generation and electric field manipulation was revealed: the basic theory of two-phase flow in the microchannel was described,and the mechanism and influencing factors of droplet formation based on co-flow method and simulation results was analyzed.According to the characteristics of the dielectric in the electric field and the theory of the electrohydrodynamic,the mechanism and influencing factors of the controllable release of guided microcapsules by electric fields was also analyzed,laying the theoretical basis for the further experiments.Secondly,the experiments of guided microcapsules generation was conducted: a glass capillary microfluidic chip was designed and processed for the generation of doubleemulsion droplets,with controllable number and size of cores.The effect of each phase flow rate on the size and numbers of inner core of double-emulsion droplets,and the flow rate range suitable for the fabrication of double-emulsion droplets with two inner cores was determined.Then,monodisperse guided microcapsules with two inner cores were prepared,and one of which is a magnetic core.Thirdly,manipulation experiments of guided microcapsules was developed: a microfluidic chip with electrode substrates was designed and processed,and targeted delivery experiments of guided microcapsules by an external magnetic field was implemented.Under the effect of the external alternating electric field,the controlled release of the single core of the guided microcapsule was realized while the magnetic core remained intact.The influence of the electric field parameters on the release behavior of the guided microcapsule was measured,and the experimental phenomena were analyzed and summarized.Then,the magnetic field was again applied to achieve the evacuation of the released microcapsules.Finally,the application experiments of guided microcapsules in the field of particle delivery and manipulation was conducted: the microfluidic chip used in the experiment was designed and processed,and the guided microcapsules containing fluorescent particles was fabricated.By applying the external magnetic field,the long-distance targeted delivery of the fluorescent particles and the evacuation of the released microcapsules were achieved;under the effect of the external electric field,the controlled release and collection experiments of fluorescence particles were realized,besides the experimental phenomena were analyzed combined with the simulation.In this study,we proposed a guided microcapsule structure and a controlled release method,which has the advantages of simple operation,no pollution and wide application and so on.It provides a new approach to achieve the drugs delivery.