Study On Morphology Control And Application Of Three Dimensional Electrospraying/Electrospinning Membrane Materials

Electrospraying and electrospinning are important technologies for rapid and continuous production of micro/nano particles/fibers.Electrospraying is used to prepare particulates and porous coatings.Electrospinning is used to fabricate three dimensional fiber membrane with interpenetrating pores.Their equipment is cheap and easy to operate.It has wide applications in many fields such as biomedicine,energy storage materials,photoelectric devices,filtration and adsorption.However,due to the simple structure and single performance of membrane materials,the further application of continuous particles or fibers is limited.Biofilms with different pore sizes exist in natural organisms,which show unique structures and properties after a long period of evolution.Inspired by the existence of biofilms in nature,the morphology and structure of particles/fibers can be controlled by the design of electrospraying/electrospinning raw fluid composition and the adjustment of processing parameters.Three-dimensional membrane materials with diverse topological structures can be obtained,giving them unique intelligent responsiveness in specific environments.It provides a new way to solve the problems in the practical application of porous membrane materials.Inspired by some common substances in nature,we successfully prepared particles/fibers with unique morphology combined with electrospraying and electrospinning technology by adjusting the composition of different polymers and processing parameters.We obtained functional composite membrane materials,explored the relationship between microstructure and performance,and developed bionic intelligent materials with excellent performance.The main research content is divided into the following two parts:(1)The red blood cells in the blood are a kind of round shape with concave sides.Its unique shape can easily through the thinnest place in the capillaries and transport oxygen and nutrients to any part of the body.In this study,PLA and PVP,two nontoxic polymers,were selected to study the effect of mass ratio of the two polymers on the properties of the solution.With the different content of PVP,three kinds of particles with different morphology were obtained: spindle-like,red-blood-cell-like and disk-like.This is due to the discontinuous small droplets in the electric field.During the solidification process,the volatilization speed of the internal and external solvents of the droplets is different,and the concentration difference is formed.The internal solution is replenished to the outside,resulting in the center depression and the formation of red-blood-cell-like particles.With the increase of PVP content,the viscosity decreased,and the fluidity of the solution became better.When the internal solvent is replenished to the outside,the external solvent volatilizes in time and disk-like particles formed.The microstructure of the particles was analyzed by TEM and XPS.It was found that the phase separation of the two polymers occurred during the electrospinning process.The PVP with low surface energy migrated out spontaneously and gathered on the surface of the particles to form a shell layer.Furthermore,the core-shell structure of PLA/PVP particles was confirmed by deionized water treatment.Finally,we tested the cytotoxicity of PLA/PVP microparticles by MTT method,and the cytotoxicity of PLA/PVP microparticles with different proportions was lower.Therefore,the red-blood-cell-like particles with core-shell structure prepared by single needle have potential applications in drug loading.(2)Desert beetles can survive in the desert,mainly due to the hydrophilic texture on their wings catching water in the air and the hydrophobic groove below transports water to their mouth.Imitating the structure of desert beetles wings and their strong ability to capture moisture in the air,we prepared a PVA-PLA hierarchical membrane to capture water in the fog.The top layer was composed of water-chestnut-like PVA particles by electrospraying.During electrospraying,PVA solution with low concentration was not easy to form continuous jet but many small droplets.These droplets were mainly affected by gravity and electric field force in the electric field.Because the electric field force was far greater than gravity,the droplets were stretched rapidly in the electric field direction,and formed sharp angular edge in the direction of electric field force.However,deionized water as solvent had poor volatility.When the droplets solidified,they continued to flow downward under the action of gravity,and arc-shaped edge in the direction of gravity was formed.Thus,water-chestnut-like particles was obtained.The bottom layer was composed of electrospun PLA fiber.The PLA fiber film had highly oriented because the rotating drum was used as the receiving device.During the fog collection process,the top layer of PVA cooperated with the bottom layer of PLA.The top water-chestnut-like PVA particles had a large surface area,which was conducive to the water droplets in the fog to attach and condense on it.It could improve the speed of receiving fog.The PLA fiber of the bottom layer provided a guide channel for the water droplets,which could transport the collected water droplets faster.This kind of functional composite membrane could effectively improve the efficiency of fog collection,which provided a new idea for solving the global shortage of fresh water resources.