| Because of its high surface area and excellent mechanical properties,nanofibers can be widely used in the fields of sensors,biomedicine,energy and so on.Electrospinning is one of the most important methods for manufacturing nanofibers,while there are some difficulties for electrospinning in mass production.For multi-nozzle or multi-hole electrospinning,adjacent jets show interference with each other and can be easily clogged.Free surface electrospinning depending on special shapes of electrodes or introducing disturbance to the solution surface also suffers the drawbacks such as electrode passivation and poor morphology of nanofibers.Therefore,this paper proposed noncontact rod induced electrospinning method,using a rod moving above plane free solution surface,lots of tiny jets will be generated on the solution surface under the rod because of the high elecrtric field.After the rod moves away,the jets will be stretched and whip with solvent evaporation,then turn into nanofibers and deposit on the grounded collector.The paper focus on the basic technological rule of noncontact rod induced electrospinning,mechanism analysis of fluid motion and device design for noncontact rod induced electrospinning,which lays the foundation for developing noncontact rod induced electrospinning device for mass production.The main contents of this paper are presented as follows:(1)The inducing properties with different rod materials were analyzed.The roles of the dielectric and conductive properties of rod played in enhancing the electric field and charge density were also investigated.The finite element analysis of electric field and the experiments results showed that the conductivity of the rod played the main important role in inducing jets,and the rod with a resistance of 107?1010? can induce jets.What's more,this paper investigated the rules of noncontact rod-induced electrospinning process,especially on the factors which influence the critical voltage.It explored the correlation between the current across the rod and the applied voltage/the resistance of rod/moving speed of rod.(2)The paper introduced the basic theory of electrohydrodynamics,and analyzed the correspondences between the fluid surface deformation and the fluid speed/electrical stress in the fluids.We conducted the simulation with different inducing distance,applied voltage and solution properties to evaluate their influence on generating jets,and the simulation results show great agreement with experiments.In addition,a moving mesh method was used to investigate the earlier deformation of the interface caused by the moving rod,showing the importance of charge migration resulted from rod movement in generating multi-jets.(3)We developed the automated noncontact rod-induced electrospinning device,whose rod can move above the reservoir while rotating.The throughput of the setup was measured and the morphology of nanofibers was analyzed with different solution concentration,voltage,inducing distance,rod speed and collecting distance using this automated device.The results showed that the optimized electrospinning parameters for PEO solution should be as follows:solution concentration of 12%wt,applied voltage of 60kV and collecting distance of 35cm.By these optimized conditions,the diameter of nanofiber with nice morphology ranged from 50nm to 400nm.The maximum throughput of the device can reach 61.7 g/m2-h. |
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