Preparation Of Core-shell And Janus Microspheres With Microfluidic Technology

Microfluidics(microfluidics)refers to the science and technology of precise manipulation of tiny volumes of fluids using channels with sizes of tens to hundreds of micrometers,and is a new interdisciplinary formed by of the combination of Chemistry,chemical engineering,MEMS and fluid mechanics.Devices that integrate tiny channels and specific functional units are called microfluidics chips.The use of microfluidic technology to prepare emulsion droplets has the advantages of precise structure control,good monodispersity,and fast preparation speed.Using emulsion droplets as a template to prepare micro-particle materials with specific functions is one of the focus of current microfluidic technology development.This paper comprehensively discusses the advantages of microfluidic technology for preparing emulsion droplets and functional materials,and uses two microfluidic chips with different structures to prepare core-shell microspheres and Janus microspheres.The main research contents are as follows:(1)A series of core-shell polymer microspheres with hierarchical pore structure were prepared using a sleeve-type microfluidic chip.By adding undecyl alcohol to the photo-curable resin,phase separation occurs in the process initiated by ultraviolet light to obtain a pore structure.Further,the size and the wall thickness of the polymer microspheres were adjusted by adjusting the flow rates of different phases.We can obtain polymer microspheres with a wall thickness of 40-100 μm and a size of 350-440 μm.The obtained polymer microspheres were plated with silver by a chemical deposition method to become polymer-silver hybrid microspheres.The hybrid microspheres were calcined to obtain silver shell hollow microspheres.It was used for SERS research.Through experiments and numerical simulations,it was verified that the aggregation state of the silver nanoparticles changed significantly during the calcination process,which affected the SERS effect of the microspheres.The hollow porous structure is beneficial for SERS detection by enhancing the deposition of silver in the microspheres and making a particular gap between the silver particles The experimental and simulation methods used in this work provide a useful reference for the preparation of other functional porous microsphere materials with hollow structures.(2)By using a simple unipolar microfluidic chip,liquid paraffin and chitosan-nanoparticles are used as continuous phases and well-dispersed phases.By adjusting the flow rate of the two,W / O emulsified droplets are generated,which are cured to solidify the micro-droplets into microspheres.The hydrogen peroxide solution was added to the chitosan solution to adjust the viscosity of the chitosan solution,so that when the original uniform chitosan-nanoparticle micro-droplets undergo cross-linking,the nanoparticles undergo phase separation in the microdroplets.As a result,it was deposited on one end of the micro-droplet,and after curing,the chitosan-nanoparticle Janus microspheres were formed.It is concluded from the experiments that the process of nanoparticles settling and the process of chitosan and glutaraldehyde crosslinking occur simultaneously.When the speed of the sedimentation process is higher than the speed of glutaraldehyde diffusion cross-linking,Janus microspheres will be generated.In this method,simple solid-liquid two-phase phase separation can be used to prepare Janus microspheres of chitosan-nanoparticles easily quickly.The nanoparticles in this method are diverse and have good universality.