Local Modification Of Microfluidic Droplet Chip Based On Polyvinyl Alcohol Open Coating For The Preparation Of Multi-layer Hydrogel Microcapsules

The multi-layer microcapsules has a multi-layer structure,can achieve individual encapsulation of a variety of substances,and has wide application value in the fields of cancer treatment,tissue regeneration and enzymatic reaction.Due to the particularity of the size and structure of the microcapsules,the microcapsules prepared by the macroscopic scale equipment are difficult to meet the requirements of monodispersity and complex structure,and limit their further application.Microfluidic droplet technology can produce multilayer droplets with controllable structure and size.Using multi-layer droplets as templates,multi-layer microspheres with uniform size and controllable structure can be further prepared,which is a good choice for developing multi-layer microcapsules preparation technology.However,current microfluidic droplet technology still has limitations in the synthesis of multi-layer microcapsules.Polydimethylsiloxane(PDMS)is a commonly used material for preparing microfluidic droplet chips.The surface is hydrophobic.The formation of multi-layer droplets requires that the chip part channel be hydrophilic,so it is necessary to partially modify the surface.However,the local modification processing technology for PDMS microfluidic multi-layer droplet chips is generally complicated and limited in versatility,which limits the application of this method in the preparation of multi-layer microcapsules.This paper proposes a method based on polyvinyl alcohol(PVA)open coating,which can quickly and simply realize the local modification of the microchannel surface of PDMS microfluidic chip,and then form multi-layer droplets with complex structure.Using multi-layered droplets droplets as templates,multi-layer hydrogel microcapsules can be successfully synthesized.In the first chapter,firstly,the definition of microcapsules,and the preparation method of multi-layer microcapsules are summarized.Secondly,the microfluidic droplet technology,the method of generating droplets and the method of generating multi-layer droplets are introduced.Thirdly,the surface modification technology of commonly used PDMS microfluidic chip is summarized.Finally,the purpose and design idea of this paper are put forward.In the second chapter,the PVA open coating is used to locally modify the flow focusing microfluidic droplet chip.Firstly,the chip layer of PDMS microfluidic droplet chip was designed and fabricated by soft lithography.Then it was partially modified by PVA open coating and finally sealed to obtain a flow focusing microfluidic chip with clear hydrophilic and hydrophobic microchannels.Secondly,the concentration of PVA solution was optimized,and the PVA coating process was exhibited.The controllability of PVA open coating method was verified.The modification method is manually completed,requires only one reagent,has the characteristics of being simple,fast,and reliable,and does not require complicated instruments and equipments,and has generalization.In the third chapter,using the prepared flow-focusing microfluidic chip with local hydrophilic and hydrophobic regions,multi-layer droplets were formed and used as templates to prepare different layers of multi-layer calcium alginate microcapsules and multi-layer chitosan microcapsules.The prepared microcapsules have stable interface and clear morphology,and the variation coefficient values of the particle size distribution are less than 3%,and have high monodispersity.The pH response of multi-layer chitosan microcapsules was investigated.In the fourth chapter,the PVA open coating modification method proposed in this paper is summarized,and its application prospect in processing other complex surface wetting mode chips and preparing other functional multi-layer core-shell particles with complex structures is prospected.