Abstract:

Objective Aiming at the existing problems of multi-needle electrospinning and needleless electrospinning, petal shaped electrospinning nozzle with multiple tips is proposed and used as the emitting electrode. In the electrospinning process, the structure of the emitting electrode has a great influence on the intensity and distribution of the electric field, and has been an important research object. Therefore, it is necessary to design a new electrospinning emitting electrode and optimize the specific parameters of the new emitting electrode.

Method The nozzle was designed as a semi-closed structure. The upper part was divided into a cylindrical straight pipe multi-channel structure, using the method of equal cross-sectional area of each channel, so as to divide the flow evenly while slowing down the flow speed. The lower part was divided into petal shaped flow channel expansion structure. The curve of petal shaped flow channel was designed by Bezier curve, and the end of the petal was the tip to stimulate multiple jets under low energy consumption. COMSOL finite element analysis software was used to simulate the three-dimensional electric field and find the improved methods of increasing the field intensity and reducing end effect. Finally, experiments were carried out validate of the model.

Results The distribution and change of electrospinning electric field of the new type of electrospinning nozzle were simulated. With the increase of the number of petals, the average electric field intensity of the petal tip decreases from 4.446×10⁶ V/m to 3.336×10⁶ V/m due to the fact that the coulomb repulsion interaction between petals became more obvious, suggesting that the number of petals should not be too many. By comparing the electric field intensity and CV value at the tip of different petal lengths, the field was most uniform when there were four pairs of petals. When the length of the outer petal was fixed, the electric field intensity CV value of the petal tip all showed a trend of decreasing first to a certain value and then increasing with the length of the inner petal changing from short to long. Compared with the parameter models with the best electric field CV value in each group, under the condition that the droplet was fully spread and formed normally, the electric field CV value was the best when the inner petal length was 20 mm and the outer petal length was 21 mm, and the value was 6.74%. The capillary effect was used to widen the petals and the distance between each petal was 4 mm, in order to drain the liquid supply and prevent the solution from leaking in the gap between the petals. After the petal dislocation arrangement, the average electric field intensity became 5.441×10⁶ V/m, and the electric field intensity CV value reached 5.58%, indicating that increasing the average distance between petal tips can effectively improve the uniformity of the electric field intensity. Finally, the metal 3D printing nozzle was used for experimental verification, and the fiber film was obtained. Surface morphology and fiber diameter distribution were examined by Hitachi Flex SEM1000 cold field scanning electron microscope, and the average diameter of the fibers was 258.69 nm with CV value being 15.54%.

Conclusion Petal shaped electrospinning nozzle with multiple tips is proposed in this paper. The optimal structural parameters are 4 pairs of petals, 21 mm length of inner petals, and 20 mm length of outer petals, together with the dislocation arrangement of inner and outer petals. The finite element analysis shows that the new nozzle can effectively combine the advantages of needle and needle-free electrospinning, produce high field intensity and uniform distribution of electrostatic field and can effectively avoid solution volatilization and environmental pollution. The experimental results show that each tip of the petal-like multi-tip electrospinning nozzle can produce a stable and continuous jet, and the total spinning area is large, and the generated fibers are fine and uniform.

Key words: electrospinning, petal-shaped nozzle, multi-tip, COMSOL, electric field simulation