Research Of Controllable Multi-jets Needle-disk Electrospinning And Its Application In Oil-water Separation

Due to the high surface area,high porosity,collection between pores,controllable fiber diameter and membrane thickness,nanofiber membrane has been used in tissue engineering,filtration,optical/electrical device,sensors and so on.E lectrospinning is regarded as the straight and simplest method to fabricate nanofibers.However,the drawback of low productivity of electrospinning has not been well dissolved up to now.Firstly,we put forward the needle-disk electrospinning based on t he analysis of “Taylor-cone” of traditional single needle electrospinning(TNE),the bubble rupture of bubble electrospinning and inspired by the phenomenon of natural “point discharge”.Needle-disk electrospinning can significantly improve the nanofiber productivity at low voltage supply.The spinneret of needle-disk electrospinning is adding the metal needle on the disk(spinneret of the disk electrospinning).Previous methods spinning from free liquid surface need high voltage supply to wave the polymer solution,form the “Taylor like-cone” and initiate the charged jets.The jet initiation is a “passive” process.However,the needles covered by a liquid film,reminiscent of “Taylor-cone”,provide the sites of jet initiation,showing an “active” process of Taylor-cone formation.What’s more,the needle tips make the needle-disk high curvature,high density of surface charge,and of course,high intensity of electrical field,making the possibility of fabricating nanofiber under lower voltage supply.Through the numerical simulation method with the practical experimental,we systematically investigate the effect of spinning parameters on the spinning process;then,put forward the principle of needle-disk electrospinning and conclude the spinning process of this method.From the results of numerical simulation,needle-disk electrospinning induces 11.8 times of electrical field intensity than that of disk electrospinning under same parameters.The diameter of nanofiber fabricated by needle-disk electrospinning is 245±33nm,while the disk electrospinning is 463±89nm.Meanwhile,the experimental results show that needle-disk electrospinning can fabricate competitive nanofiber as TNE can do;and 183 times of nanofiber productivity than TNE.What’s more,the fiber diameter and productivity can be controlled by easily adjusting the spinning parameters.Therefore,needle-disk electrospinning can fabricate nanofiber with high quality and high throughput under low voltage supply.Secondly,based on t he parameter optimizing of needle-disk electrospinning,the effluence of binary solvent(low/high volatility)and humidity on the formation of wrinkled surface of nanofiber are systematically investigated.The fiber surface morphology and diameter can be changed by adjusting the ratio of binary solvent and humidity.Based on the previous study and experimental,we put forward the mechanism of forming the wrinkle surface of nanofiber and point out that binary solvent with low/high volatility provide the time to form the solvent-rich phase and polymer-rich phase.In other words,the process of solvent evaporation is stable using single solvent,which contributes to the formation of smooth fiber.Once formed the solvent-rich and polymer-rich phase under binary solvent,the jets solution turn to solid fiber where the water replace the solvent with high volatility.Therefore,hierarchical wrinkle surface nanofiber is prepared.Subsequently,super-hydrophobic PMMA,PVDF-HFP nanofiber are prepared and applied to oil-water separation.Finally,based on t he parameter optimizing of needle-disk electrospinning,CuO nano-sheet was successfully grown on t he surface of PVDF-HFP nanofiber using the electrospinning method,heat treatment and hydrothermal method.Due to the natural hydrophilicity and rough surface of CuO nano-sheet,the resulting hybrid organic/inorganic nanofiber membrane shows superhydrophilic property.Then,we proposed the mechanism of preparing the functional superhydrophilic membrane.From the experimental results,we know that the CuO beads prepared after heat treatment process is the key point of growing CuO nano-sheet;and the growth temperature has great effect on the CuO morphology.The superhydrophilic and underwater superoilephobic membrane(the underwater oil contact angle is 152.4°)can be used to oil-water separation.The results show that the functional membrane exhibit excellent separation efficiency(better than 99.80%)of oil-water emulsion in which the size of oil droplet large than 1μm.In summarize,needle-disk electrospinning can fabricate high quality,various polymer nanofibers with high throughput,under low voltage supply,which is helpful to the industrialization and application of nanofiber.What’s more,we propose the formation mechanism of wrinkle surface of nanofiber under binary solvent.This mechanism has a guiding significance to fabricate rough surface nanofiber with special wet-ability property.Additionally,superhydrophilic and underwater superoilephobic membrane is prepared and exhibits excellent separation efficiency of emulsifying oil-water mixture in which the size of oil droplet large than 1μm.Meanwhile,the proposed mechanism is beneficial for preparing functional hybrid organic/inorganic nanofiber membrane.