A statistical analysis on the influence of process and solution properties on centrifugally spun nanofiber morphology

Centrifugal spinning is a fast and safe nanofiber production technique and polyacrylonitrile (PAN) nanofibers have been widely studied for many applications including energy storage, filtration, sensors, and biomedical applications. Nanofiber morphology, specific surface area, porosity and average fiber diameter are important to determine the performance of nanofibers in these fields. In centrifugal spinning, nanofiber morphology and average fiber diameter are influenced by solution properties and process parameters including rotational speed, feeding rate, collector distance, and nozzle diameter. In this study, the effect of solution concentration, rotational speed, feeding rate, collector distance and nozzle diameter on average fiber diameter and fiber morphology were studied and statistical analysis was performed to determine the main factors. Optimum solution and process parameters were determined as well. Increased average fiber diameter was seen with increasing polymer concentration and nanofibers produced at 4000 rpm with the feeding rate of 60 ml/h had the lowest average fiber diameter for all studied nozzle sizes (0.3 mm, 0.5 mm and 0.8 mm). 8 wt. % PAN solution was centrifugally spun with the rotational speed of 4000 rpm, feeding rate of 60 ml/h, collector distance of 20 cm and nozzle diameter of 0.3 mm and bead free nanofibers with the average fiber diameter of 680 ± 87 nm was observed.

Needle-disk Electrospinning: Mechanism Elucidation, Parameter Optimization and Productivity Improvement

Background: Nanofiber’s productivity plagues nanofibrous membranes’ applications in many areas. Herein, we present the needle-disk electrospinning to improve throughput. In this method, multiple high-curvature mentals are used as the spinning electrode. Methods: Three aspects were investigated: 1) mechanism elucidation of the needle-disk electrospinning; 2) parameter optimization of the needle-disk electrospinning; 3) productivity improvement of the needle-disk electrospinning. Results: Results show that high-curvature electrode evokes high electric field intensity, making lower voltage supply in spinning process. The needle number, needle length and needle curvature synergistically affect the spinning process and nanofiber morphology. Additionally, higher disk rotation velocity and higher voltage supply can also result in higher nanofiber’s productivity. Conclusion: Compared with previous patents related to this topic, the needle-disk electrospinning is featured with the merits of high throughput, low voltage supply, controllable spinning process and nanofiber morphology, benefiting the nanofiber practical industrial employment and further applications of nanofiber-based materials.

Effect of Silk Sericin Content on the Electrospun Silk Nanofibrous Membrane Property

Aims: Research of the effect of silk sericin content on the morphology and structure of electrospun silk nanofibrous membrane. Background: Silk sericin has significant influence on the silk solution and regenerated silk-based materials property, while few reports were found to investigate. Objective: We'll know the effect of silk sericin content on the morphology and structure of electrospun silk nanofibrous membrane. Methods: Four degumming conditions (none degumming, boiling water degumming, 0.05 % Na2CO3 degumming, 0.5 % Na2CO3 degumming) were carried out a systematic investigation in terms of silk sericin content after degumming, regenerated silk nanofibrous membrane morphology (SEM) and structure property (FTIR, XRD). Result: The results show that 0.5 % Na2CO3 degumming results poor spinnability. The solution derives from none degumming and boiling water degumming present high viscosity, leading to a hard silk nanofiber fabrication process. The silk nanofiber from the 0.05 % Na2CO3 degumming shows easier fabrication process and better nanofiber morphology. Conclusion: We successfully prepared silk nanofiber membrane with different sericin content. The sericin content significantly affects the spinnability and subsequent nanofiber morphology. Higher sericin content leads to poor solution spinnability and numerous droplets on resulting nanofiber membrane. Additionally, the sericin can both existence of structural silk I and silk II, which will favor to the increase of mechanical property.

The crown ether size and stereochemistry affect the self-assembly, hydrogelation, and cellular interactions of crown ether/peptide conjugates

Crown ether ring size affects nanofiber morphology of hydrogels upon conjugation with D- and L-phenylalanine dipeptides. Random nanofibers showed enhanced cell adhesion and proliferation whereas twisted nanofibers displayed weak cell attachments.

Electrospun Jets Number and Nanofiber Morphology Effected by Voltage Value: Numerical Simulation and Experimental Verification

Electrical voltage has a crucial effect on the nanofiber morphology as well as the jet number in the electrospinning process, while few literatures were found to explain the deep mechanism. Herein, the electrical field distribution around the spinning electrode was studied by the numerical simulation firstly. The results show that the electrical field concentrates on the tip of a protruding droplet under relatively low voltage, while subsequently turns to the edge of needle tip when the protruding droplet disappears under high voltage. The experimental results are well consistent with the numerically simulated results, that is, only one jet forms at low voltage (below 20 kV for PVDF-HFP and PVA nanofiber), but more than one jet forms under high voltage (two jets for PVDF-HFP nanofiber, four jets for PVA nanofiber). These more jets lead to (1) higher fiber diameter resulting from actually weaker electrical field for each jet and (2) wide distribution of fiber diameters due to unstable spinning process (changeable jet number/site/height) under high voltage. The results will benefit the nanofiber preparation and application in traditional single-needle electrospinning and other electrospinning methods.

Effects of cylindrical-electrode-assisted solution blowing spinning process parameters on polymer nanofiber morphology and microstructure

Cylindrical-electrode-assisted solution blowing spinning (CSBS) is a novel method for preparing polymer nanofibers by using air-stretch and electrostatic simultaneously, which can fabricate thinner and more uniform nanofibers than the traditional solution blowing spinning (SBS). In this work, the effects of processing parameters including length of cylinder (LC), needle to cylinder distance (NCD) and left face of cylinder to collector distance (CCD) on the CSBS nanofiber diameter were investigated. The results are as follows: when the NCD decreased, the fiber diameter decreased; when the LC increased, the fiber diameter decreased; the CCD didn’t significantly affect the fiber diameter. Moreover, an orthogonal experimental design was utilized to investigate the effect of injection rate, air pressure, NCD, LC, diameter of cylinder (DC), voltage and CCD on the fiber diameter and porosity of various surface layers of nanofiber web (P1, P2, and P3). The results showed that the varied range of each properties (average diameter, standard deviation of the diameter, P1, P2, and P3) was 539.121-904.149 nm, 127.903-303.253, 71.464-85.1415%, 60.32725-75.46625%, 48.23925-70.08875%, respectively. We also found the order of the influence of the above-mentioned seven process parameters on each above properties of the nanofiber web, and the corresponding optimal spinning process parameters were listed. It is well known that the fiber diameter affects the mechanical properties of nanofibers, and porosity of nano-fiber webs is an important parameter in tissue engineering, bioengineering, and filtration. The effects of CSBS process parameters on nanofiber morphology and microstructure were investigated for the first time. The conclusion of the paper can help researchers to produce high quality CSBS nanofiber and promote the wider application of this novel technology.