scholarly journals Melt Electrospinning Writing Process Guided by a “Printability Number”

2017 ◽  
Vol 139 (8) ◽  
Author(s):  
Filippos Tourlomousis ◽  
Houzhu Ding ◽  
Dilhan M. Kalyon ◽  
Robert C. Chang
Keyword(s):  
Three Dimensional ◽  
Polymer Melt ◽  
Volumetric Flow Rate ◽  
Thermal Conditions ◽  
Electrospinning Process ◽  
Critical Parameters ◽  
Experimental Investigations ◽  
Dimensionless Numbers ◽  
Melt Electrospinning ◽  
Resistive Forces

The direct electrostatic printing of highly viscous thermoplastic polymers onto movable collectors, a process known as melt electrospinning writing (MEW), has significant potential as an additive biomanufacturing (ABM) technology. MEW has the hitherto unrealized potential of fabricating three-dimensional (3D) porous interconnected fibrous mesh-patterned scaffolds in conjunction with cellular-relevant fiber diameters and interfiber distances without the use of cytotoxic organic solvents. However, this potential cannot be readily fulfilled owing to the large number and complex interplay of the multivariate independent parameters of the melt electrospinning process. To overcome this manufacturing challenge, dimensional analysis is employed to formulate a “Printability Number” (NPR), which correlates with the dimensionless numbers arising from the nondimensionalization of the governing conservation equations of the electrospinning process and the viscoelasticity of the polymer melt. This analysis suggests that the applied voltage potential (Vp), the volumetric flow rate (Q), and the translational stage speed (UT) are the most critical parameters toward efficient printability. Experimental investigations using a poly(ε-caprolactone) (PCL) melt reveal that any perturbations arising from an imbalance between the downstream pulling forces and the upstream resistive forces can be eliminated by systematically tuning Vp and Q for prescribed thermal conditions. This, in concert with appropriate tuning of the translational stage speed, enables steady-state equilibrium conditions to be achieved for the printing of microfibrous woven meshes with precise and reproducible geometries.

scholarly journals A New Three-Dimensional Mobile Magnetic Melt Spinning Device

2021 ◽  
Author(s):  
Kai Zhang ◽  
Wu Zhao ◽  
Qingjie Liu ◽  
Miao Yu
Keyword(s):  
Electric Field ◽  
High Voltage ◽  
Melt Spinning ◽  
Three Dimensional ◽  
Fiber Surface ◽  
Electrospinning Process ◽  
Superior Performance ◽  
Fiber Morphology ◽  
High Voltage Power Supply ◽  
Melt Electrospinning

Abstract The size and morphology of nanofibers directly determine their application scope and performance, while regular patterned fibers further demonstrate their superior performance in the field of sensors and biomaterials. Melt electrospinning enables controlled deposition of fibers and is currently one of the most important means of preparing patterned fibers. However, due to the existence of high-voltage electric field, melt electrospinning has safety problems such as partial discharge and electric field breakdown, coupled with the charge rejection on the fiber surface, which seriously affects the positioning deposition of fibers and makes it difficult to obtain regular patterned fibers, greatly limiting the application areas and application effects of patterned fibers. Therefore, the improvement and innovation of the spinning process is particularly urgent. Based on material-field model and contradiction matrix of TRIZ theory, the problems of melt electrospinning device are systematically analyzed. The technical conflicts are solved by the inventive principles. A three-dimensional mobile magnetic melt spinning device model is constructed, a magnetic spinning test prototype is developed, and the prototype performance and influencing factors are studied by fiber morphology. The results show the following: (1) Replacing electrostatic fields with permanent magnetic fields can fundamentally avoid safety hazards such as electric field breakdown. (2) The magnetic field force on the molten polymer fluid can generate enough stretching force to overcome the surface tension and form fibers. (3) The fibers are deposited without a whipping instability phase similar to the electrospinning process, allowing easy preparation of regular patterned fibers. (4) The planar motion of the collector creates additional stretching effect on the fibers, which can further reduce the fiber diameter. (5) In magnetic spinning, no external high-voltage power supply is required, enabling the portability of the device. The results of this paper can provide a new method for preparing nanofibers with patterned morphology.

scholarly journals The Effect of Dye and Pigment Concentrations on the Diameter of Melt-Electrospun Polylactic Acid Fibers

Polymers ◽  
2020 ◽  
Vol 12 (10) ◽  
pp. 2321 ◽  
Author(s):  
N.K. Balakrishnan ◽  
K. Koenig ◽  
G. Seide
Keyword(s):  
Electrical Conductivity ◽  
Polylactic Acid ◽  
Electrical Resistance ◽  
Polymer Melt ◽  
High Viscosity ◽  
Electrospinning Process ◽  
Polymer Aggregates ◽  
Melt Electrospinning ◽  
Coarse Fibers ◽  
Solution Electrospinning

Sub-microfibers and nanofibers produce more breathable fabrics than coarse fibers and are therefore widely used in the textiles industry. They are prepared by electrospinning using a polymer solution or melt. Solution electrospinning produces finer fibers but requires toxic solvents. Melt electrospinning is more environmentally friendly, but is also technically challenging due to the low electrical conductivity and high viscosity of the polymer melt. Here we describe the use of colorants as additives to improve the electrical conductivity of polylactic acid (PLA). The addition of colorants increased the viscosity of the melt by >100%, but reduced the electrical resistance by >80% compared to pure PLA (5 GΩ). The lowest electrical resistance of 50 MΩ was achieved using a composite containing 3% (w/w) indigo. However, the thinnest fibers (52.5 µm, 53% thinner than pure PLA fibers) were obtained by adding 1% (w/w) alizarin. Scanning electron microscopy revealed that fibers containing indigo featured polymer aggregates that inhibited electrical conductivity, and thus increased the fiber diameter. With further improvements to avoid aggregation, the proposed melt electrospinning process could complement or even replace industrial solution electrospinning and dyeing.

scholarly journals Size-Controllable Melt-Electrospun Polycaprolactone (PCL) Fibers with a Sodium Chloride Additive

Polymers ◽  
2019 ◽  
Vol 11 (11) ◽  
pp. 1768 ◽  
Author(s):  
Piyasin ◽  
Yensano ◽  
Pinitsoontorn
Keyword(s):  
Electrostatic Force ◽  
Electrospun Fiber ◽  
Polymer Melt ◽  
High Viscosity ◽  
Electrospinning Process ◽  
Electrospun Fibers ◽  
Glass Syringe ◽  
Melt Electrospinning ◽  
Size And Morphology ◽  
Two Parameters

Melt-electrospun polycaprolactone (PCL) fibers were fabricated by using NaCl as an additive. The size and morphology of the PCL fibers could be controlled by varying the concentration of the additive. The smallest size of the fibers (2.67 0.57) µm was found in the sample with 8 wt% NaCl, which was an order of magnitude smaller than the PCL fibers without the additive. The melt-electrospun fibers were characterized using the differential scanning calorimeter (DSC), X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FTIR) techniques. Interestingly, a trace of NaCl was not found in any melt-electrospun fiber. The remaining PCL after melt-electrospinning was evaporated by annealing, and the NaCl residual was found in the glass syringe. The result confirmed that the NaCl additive was not ejected from the glass syringe in the melt-electrospinning process. Instead, the NaCl additive changed the viscosity and the polarization of the molten polymer. Two parameters are crucial in determining the size and morphology of the electrospun fibers. The higher NaCl concentration could lead to higher polarization of the polymer melt and thus a stronger electrostatic force, but it could also result in an exceedingly high viscosity for melt-electrospinning. In addition, the absence of NaCl in the melt-electrospun PCL fibers is advantageous. The fibers need not be cleaned to remove additives and can be directly exploited in applications, such as tissue engineering or wound dressing.

scholarly journals A new magnetic melt spinning device for patterned nanofiber

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Kai Zhang ◽  
Wu Zhao ◽  
Qingjie Liu ◽  
Miao Yu
Keyword(s):  
Electric Field ◽  
High Voltage ◽  
Melt Spinning ◽  
Three Dimensional ◽  
Fiber Surface ◽  
Electrospinning Process ◽  
Superior Performance ◽  
Fiber Morphology ◽  
High Voltage Power Supply ◽  
Melt Electrospinning

AbstractThe size and morphology of nanofibers directly determine their application scope and performance, while regular patterned fibers further demonstrate their superior performance in the field of sensors and biomaterials. Melt electrospinning enables controlled deposition of fibers and is currently one of the most important means of preparing patterned fibers. However, due to the existence of high-voltage electric field, melt electrospinning has safety problems such as partial discharge and electric field breakdown, coupled with the charge rejection on the fiber surface, which seriously affects the positioning deposition of fibers and makes it difficult to obtain regular patterned fibers, greatly limiting the application areas and application effects of patterned fibers. Therefore, the improvement and innovation of the spinning process is particularly urgent. Based on material-field model and contradiction matrix of TRIZ theory, the problems of melt electrospinning device are systematically analyzed. The technical conflicts are solved by the inventive principles. A three-dimensional mobile magnetic melt spinning device model is constructed, a magnetic spinning test prototype is developed, and the prototype performance and influencing factors are studied by fiber morphology. The results show the following: (1) Replacing electrostatic fields with permanent magnetic fields can fundamentally avoid safety hazards such as electric field breakdown. (2) The magnetic field force on the molten polymer fluid can generate enough stretching force to overcome the surface tension and form fibers. (3) The fibers are deposited without a whipping instability phase similar to the electrospinning process, allowing easy preparation of regular patterned fibers. (4) The planar motion of the collector creates additional stretching effect on the fibers, which can further reduce the fiber diameter. (5) In magnetic spinning, no external high-voltage power supply is required, enabling the portability of the device. The results of this paper can provide a new method for preparing nanofibers with patterned morphology.

scholarly journals Revealing key parameters to minimize the diameter of polypropylene fibers produced in the melt electrospinning process

e-Polymers ◽  
2019 ◽  
Vol 19 (1) ◽  
pp. 330-340 ◽  
Author(s):  
Jonas Daenicke ◽  
Michael Lämmlein ◽  
Felix Steinhübl ◽  
Dirk W. Schubert
Keyword(s):  
Electrical Conductivity ◽  
Fiber Diameter ◽  
Sodium Stearate ◽  
Polymer Melt ◽  
Electrospinning Process ◽  
Climate Chamber ◽  
Melt Electrospinning ◽  
P 16 ◽  
Chamber Temperature ◽  
Nanoscale Fibers

AbstractThis study deals with the subject of optimizing the melt electrospinning process of polypropylene with the aim of producing nanoscale fibers. A feasibility study with two polypropylene types and different additives to adapt the material composition is performed. The polypropylene types are of different molar masses to adapt the viscosity to the process. The used additives, sodium stearate and Irgastat®P 16, have a positive effect on the electrical conductivity of the polymer melt. In addition, process parameter optimization is done by varying the climate chamber temperature, using different collector voltages and varying the nozzle-collector distance. A strong influence of the climate chamber temperature has been proven and leads to a desired temperature of 100°C. The fiber diameter is dependent on process parameters, material melt viscosity and electrical conductivity. With optimized process and material parameters, the fiber diameter could be minimized to a median value of 210 nm.

scholarly journals Structural Characterization of Receptor–Receptor Interactions in the Allosteric Modulation of G Protein-Coupled Receptor (GPCR) Dimers

2021 ◽  
Vol 22 (6) ◽  
pp. 3241
Author(s):  
Raudah Lazim ◽  
Donghyuk Suh ◽  
Jai Woo Lee ◽  
Thi Ngoc Lan Vu ◽  
Sanghee Yoon ◽  
...  
Keyword(s):  
G Protein ◽  
Protein Interactions ◽  
Metabotropic Glutamate Receptor ◽  
Three Dimensional ◽  
Allosteric Modulation ◽  
Experimental Investigations ◽  
G Protein Coupled Receptor ◽  
Metabotropic Glutamate ◽  
Gpcr Activation ◽  
G Protein Coupled

G protein-coupled receptor (GPCR) oligomerization, while contentious, continues to attract the attention of researchers. Numerous experimental investigations have validated the presence of GPCR dimers, and the relevance of dimerization in the effectuation of physiological functions intensifies the attractiveness of this concept as a potential therapeutic target. GPCRs, as a single entity, have been the main source of scrutiny for drug design objectives for multiple diseases such as cancer, inflammation, cardiac, and respiratory diseases. The existence of dimers broadens the research scope of GPCR functions, revealing new signaling pathways that can be targeted for disease pathogenesis that have not previously been reported when GPCRs were only viewed in their monomeric form. This review will highlight several aspects of GPCR dimerization, which include a summary of the structural elucidation of the allosteric modulation of class C GPCR activation offered through recent solutions to the three-dimensional, full-length structures of metabotropic glutamate receptor and γ-aminobutyric acid B receptor as well as the role of dimerization in the modification of GPCR function and allostery. With the growing influence of computational methods in the study of GPCRs, we will also be reviewing recent computational tools that have been utilized to map protein–protein interactions (PPI).

scholarly journals Online Measurement of Deposit Surface in Electron Beam Freeform Fabrication

Sensors ◽  
2019 ◽  
Vol 19 (18) ◽  
pp. 4001 ◽  
Author(s):  
Shuhe Chang ◽  
Haoyu Zhang ◽  
Haiying Xu ◽  
Xinghua Sang ◽  
Li Wang ◽  
...  
Keyword(s):  
Electron Beam ◽  
3D Reconstruction ◽  
Three Dimensional ◽  
Thermal Conditions ◽  
Online Measurement ◽  
Three Dimensional Reconstruction ◽  
Continuous Change ◽  
Position Information ◽  
Freeform Fabrication ◽  
Dimensional Reconstruction

In the process of electron beam freeform fabrication (EBF3), due to the continuous change of thermal conditions and variability in wire feeding in the deposition process, geometric deviations are generated in the deposition of each layer. In order to prevent the layer-by-layer accumulation of the deviation, it is necessary to perform online geometry measurement for each deposition layer, based on which the error compensation can be done for the previous deposition layer in the next deposition layer. However, the traditional three-dimensional reconstruction method that employs structured laser cannot meet the requirements of long-term stable operation in the manufacturing process of EBF3. Therefore, this paper proposes a method to measure the deposit surfaces based on the position information of electron beam speckle, in which an electron beam is used to bombard the surface of the deposit to generate the speckle. Based on the structured information of the electron beam in the vacuum chamber, the three-dimensional reconstruction of the surface of the deposited parts is realized without need of additional structured laser sensor. In order to improve the detection accuracy, the detection error is theoretically analyzed and compensated. The absolute error after compensation is smaller than 0.1 mm, and the precision can reach 0.1%, which satisfies the requirements of 3D reconstruction of the deposited parts. An online measurement system is built for the surface of deposited parts in the process of electron beam freeform fabrication, which realizes the online 3D reconstruction of the surface of the deposited layer. In addition, in order to improve the detection stability of the whole system, the image processing algorithm suitable for this scene is designed. The reliability and speed of the algorithm are improved by ROI extraction, threshold segmentation, and expansion corrosion. In addition, the speckle size information can also reflect the thermal conditions of the surface of the deposited parts. Hence, it can be used for online detection of defects such as infusion and voids.

Assessment of Unsteady Flows in Turbines

1992 ◽  
Vol 114 (1) ◽  
pp. 79-90 ◽  
Author(s):  
O. P. Sharma ◽  
G. F. Pickett ◽  
R. H. Ni
Keyword(s):  
Unsteady Flow ◽  
Three Dimensional ◽  
Flow Simulation ◽  
Experimental Investigations ◽  
Flow Parameters ◽  
Research Activities ◽  
Flow Features ◽  
Computational Fluid Dynamics Cfd ◽  
Turbine Design ◽  
The Impact

The impacts of unsteady flow research activities on flow simulation methods used in the turbine design process are assessed. Results from experimental investigations that identify the impact of periodic unsteadiness on the time-averaged flows in turbines and results from numerical simulations obtained by using three-dimensional unsteady Computational Fluid Dynamics (CFD) codes indicate that some of the unsteady flow features can be fairly accurately predicted. Flow parameters that can be modeled with existing steady CFD codes are distinguished from those that require unsteady codes.

Influence of a Honeycomb Facing on the Flow Through a Stepped Labyrinth Seal

2000 ◽  
Vol 124 (1) ◽  
pp. 140-146 ◽  
Author(s):  
V. Schramm ◽  
K. Willenborg ◽  
S. Kim ◽  
S. Wittig
Keyword(s):  
Flow Field ◽  
Three Dimensional ◽  
Theoretical Work ◽  
Labyrinth Seal ◽  
Honeycomb Structure ◽  
Experimental Investigations ◽  
Labyrinth Seals ◽  
Numerical Predictions ◽  
Flow Through ◽  
Aero Engines

This paper reports numerical predictions and measurements of the flow field in a stepped labyrinth seal. The theoretical work and the experimental investigations were successfully combined to gain a comprehensive understanding of the flow patterns existing in such elements. In order to identify the influence of the honeycomb structure, a smooth stator as well as a seal configuration with a honeycomb facing mounted on the stator wall were investigated. The seal geometry is representative of typical three-step labyrinth seals of modern aero engines. The flow field was predicted using a commercial finite volume code with the standard k-ε turbulence model. The computational grid includes the basic seal geometry as well as the three-dimensional honeycomb structures.

Investigations of process parameters during dissolution studies of drug loaded 3D printed tablets

2021 ◽  
pp. 095441192199358
Author(s):  
Varun Sharma ◽  
Khaja Moinuddin Shaik ◽  
Archita Choudhury ◽  
Pramod Kumar ◽  
Prateek Kala ◽  
...  
Keyword(s):  
Dissolution Rate ◽  
Process Parameters ◽  
Empirical Relation ◽  
Three Dimensional ◽  
Critical Parameters ◽  
Fused Deposition Modelling ◽  
Fused Deposition ◽  
Rate Of Dissolution ◽  
3D Printed ◽  
Percentage Release

The present research paper attempts to study the effect of different process parameters on the dissolution rate during 3D printed tablets. Three-dimensional printing has the potential of serving tailored made tablets to cater personalized drug delivery systems. Fluorescein loaded PVA filaments through impregnation route was used to fabricate tablets based on Taguchi based design of experimentation using Fused Deposition Modelling (FDM). The effect of print speed, infill percentage and layer thickness were analyzed to study the effect on rate of dissolution. Infill percentage followed by print speed were found to be critical parameters affecting dissolution rate. The data analysis provided an insight into the study of interaction among different 3D printing parameters to develop an empirical relation for percentage release of the drug in human body.

Sign in / Sign up

Export Citation Format

Share Document