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Posts Tagged ‘electrospinning’

Two new papers

Here is one new electrospinning optimization article:

Electrospinning fundamentals: optimizing solution and apparatus parameters

http://www.ncbi.nlm.nih.gov/pubmed/21304466

And new review paper:

Technological advances in electrospinning of nanofibers

http://iopscience.iop.org/1468-6996/12/1/013002

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Electrospinning process is affected by various parameters. (See my previous post) Most of the papers on parameter effect analysis are focusing on only one parameter. Since process is complex this approach has limited relevance for our goal. Some of the researchers tried to use Design of Experiments (DOE) approach in order to better understand interactions between parameters.

All articles are interested in fiber diameter. Characterization method is random selection of arbitrary number of fibers, measuring their diameter and taking average. Why is this a problem?

So here is the list of papers using DOE:

1) A design of experiments (DoE) approach to material properties optimization of electrospun nanofibres. (SR Coles et al.)

Polymer type: PVOH, PLA

Parameters studied: Conductivity (Salt-No Salt), Concentration (High-Medium-Low), Potential (High-Medium-Low), Collection distance (High-Medium-Low)

Measurements: mean fiber diameter

Conclusion: Large number of unsuccessful runs meant it was impossible to carry out a statistical analysis of this work. Interaction plots were generated for PVOH.

2) Regeneration of Bombyx mori silk by electrospinning. (S. Sukigara et al.)

Polymer type: B. Mori silk fibroin fibres

Parameters studied: Electric field (2-3-4 (kV/cm)), Concentration (12-15-16), Distance (5-7 cm)

Measurements: mean fiber diameter

Conclusion: Contour plots relating fiber diameter to electric field and solution concentration were generated for spinning distances of 5 and 7 cm.

3) Investigation on Process Parameters of Electrospinning System through Orthogonal Experimental Design. (W. Cui et al.)

Polymer type: Biodegradable poly(DL-lactide) (PDLLA)

Parameters studied: electrical voltage (15-20-25 kV), solution concentration (10-20-30 %), polymer molecular weight (50-100-165 kDa), solvent system(acetone, two other mixtures of acetone and chloroform), flow velocity (1.8-5.4-9.0 mL/h), and the needle size of syringe (0.45-0.60-0.80 mm)

Measurements: mean fiber diameter and beads percent

Conclusion: Orthogonal analysis and validation tests are performed. Quantitative equations of regression analysis could be used to prepare electrospun fibers with predetermined diameters and surface morphologies.

4) Effects of electrospinning parameters on polyacrylonitrile nanofiber diameter: An investigation by response surface methodology. (OS Yördem et al.)

Polymer type: Polyacrylonitrile (PAN)

Parameters studied: molecular weight, solution concentration, applied voltage, collector distance.

Measurements: mean fiber diameter

Conclusion: investigation the interactive effects of the parameters on the resultant fiber and to establish a prediction scheme for the domain/window of the parameters where targeted PAN fiber diameter can be achieved.

5) A new approach for optimization of electrospun nanofiber formation process. (M. Ziabari et al.)

Polymer type: Polyvinyl alcohol (PVA)

Parameters studied: solution concentration (%8-10-12), spinning distance (20-10-15 cm), applied voltage (25-20-15 kV), and volume flow rate (0.2-0.3-0.4 mL/h).

Measurements: mean fiber diameter

Conclusion: Full factorial design, 15 tests for evaluating the model, response surface plots were generated.

6) Process Optimization and Empirical Modeling for Electrospun Poly(D,L-lactide) Fibers using Response Surface Methodology (SY Gu et al.)

Polymer type: PDLA

Parameters studied: concentration (3-5-7 %), applied voltage (10-14-18 kV)

Measurements: mean fiber diameter

Conclusion: interactions between parameters is established.

7) Fabrication of electrospun poly(methyl methacrylate) nanofibrous membranes by statistical approach for application in enzyme immobilization (JP Chen et al.)

Polymer type: poly(methylmethacrylate) (PMMA)

Parameters studied: solution concentration (15-20-25-30-35 %), flow rate (0.3-0.6-0.9-1.2-1.5 ml/h), applied voltage (16-18-20-22-24 kV), temperature (10-15-20-25-30 °C), and distance (6-9-12-15-18 cm).

Meausurements: mean fiber diameter

Conclusion: establishing interactions between parameters, validating the model. Calculation of parameters for production of nanofibers with minimum diameter – 36 nm. By providing enormous surface area for C. rugosa lipase immobilization, predesigned PMMA NFM with the minimum fiber diameter could provide an enzyme loading 5.2 times the maximum values reported previously.

8 ) Prediction of water retention capacity of hydrolysed electrospun polyacrylonitrile fibers using statistical model and artificial neural network. (Dev et al.)

Polymer type: polyacrylonitrile (PAN)

Parameters studied: alkali concentration(3-6-9 5%), temperature (50-60-70°C), time (30, 45, 60).

Meausurements: mean fiber diameter

Conclusions: establishment interactions between parameters and verification of the model.

I am tracking the citations to these articles, so as soon as a new article is published I will share it here.

My favorite article is number 7 by JP Chen, because he used the knowledge of interactions to optimize fiber diameter. Other articles just established the interactions.

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Electrospinning

Electrospinning is a very easy method to produce nanofibers. All you need is a electric source, syringe, surface for collecting nanofibers. Using a pump you can feed the polymer you want to turn into fiber at a controllable rate. More than 200 polymers are proved to be suitable for electrospinning.

Here is a nice diagram from Wikipedia:

Source: http://en.wikipedia.org/wiki/File:Electrospinning_Diagram.jpg

Here are two good reviews of the subject:

Electrospinning of Nanofibers: Reinventing the Wheel?

A review on polymer nanofibers by electrospinning and their applications in nanocomposites

The problems of electrospinning

  • production rate is very low
  • we do not yet know full interactions of parameters. Most of the papers investigate the effect of only one parameter.
  • produced nanofibers are not uniform in terms of their diameter
  • formation of defected nanofibers with beads

Parameters

Solution

  • type of polymer
  • the conformation of polymer chain
  • concentration of polymer
  • elasticity
  • electrical conductivity
  • polarity
  • surface tension of the solvent

Operational

  • strength of applied electrical field
  • distance between the needle and collector
  • feeding rate
  • humidity, temperature, air velocity of the environment
  • hydrostatic pressure
  • collector composition and geometry
  • needle tip design

IE/OR applications

Some research groups used Design of Experiments to identify parameters of production

Regeneration of Bombyx mori silk by electrospinning. Part 2. Process optimization and empirical modeling using response surface methodology

Effects of electrospinning parameters on polyacrylonitrile nanofiber diameter: An investigation by response surface methodology

If you are aware of other IE/OR applications to electrospinning, please share them in comments!

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