1. Electrospinning of Nanofabrics
Presented by U6:
Pavitra Timbalia
Michael Trevathan
Jared Walker

2. Outline Introduction Background Current Research Future Research
Apparatus
General Applications
Current Research
Future Research
Questions

3. Introduction Nanofabrics are composed of nonwoven nanofibers
Nanofibers are created by a process called electrospinning.
Electrospinning is a major way to engineer (without self- assembly) nanostructures that vary in:
Fiber Diameter
Mesh Size
Porosity
Texture
Pattern Formation
Burger, Christian, et. al. Nanofibrous Materials and Their Applications

4. Introduction Grafts: Woven vs. Nonwoven
The nonwoven structure has unique features:
Interconnected pores
Very large surface-to-volume ratio
Enables nanofibrous scaffolds to have many biomedical and industrial applications.
(a) Woven fabrics
(b) Non-woven fabrics
(c) “Soldered” junctions
Burger, Christian, et. al. Nanofibrous Materials and Their Applications

5. An Example
Take the distance between the Earth and the Moon, L, to be 380,000 km.
It takes only x grams of a polymer fiber filament to make up this distance
ρ = 1 g cm-3 and the fiber diameter d = 2r = 100 nm
X = Vρ = πr2Lρ = π (50 nm)2 (380,000 km) (1 g cm-3 )
≈ 3 grams
Burger, Christian, et. al. Nanofibrous Materials and Their Applications

6. Electrospinning

7. Electrospinning - Procedure
An electrostatic potential is applied between a spinneret and a collector
A fluid is slowly pumped through the spinneret.
The fluid is usually a solution where the solvent can evaporate during the spinning.
The droplet is held by its own surface tension at the spinneret tip, until it gets electrostatically charged.
The polymer fluid assumes a conical shape (Taylor cone).
When the surface tension of the fluid is overcome, the droplet becomes unstable, and a liquid jet is ejected
Burger, Christian, et. al. Nanofibrous Materials and Their Applications

8. Burger, Christian, et. al. Nanofibrous Materials and Their Applications. 2006.

9. Burger, Christian, et. al. Nanofibrous Materials and Their Applications. 2006.

10. Burger, Christian, et. al. Nanofibrous Materials and Their Applications. 2006.

11. Types of Solvent Stream Ejections
Burger, Christian, et. al. Nanofibrous Materials and Their Applications

12. 20 wt% Poly(D,L-lactic acid) (PDLA)
Nanofibers at voltage of 20 kV, feeding rate of 20 μl min−1
20 wt%
Burger, Christian, et. al. Nanofibrous Materials and Their Applications

13. 35 wt% Poly(D,L-lactic acid) (PDLA)
Nanofibers at voltage of 20 kV, feeding rate of 20 μl min−1
35 wt%
Burger, Christian, et. al. Nanofibrous Materials and Their Applications

14. Electrospinning Polymers
Solvent
Concentration
Potential Application
Nylon 6,6
Formic Acid
10 wt%
Protective Clothing
Polyurethanes
Dimethylformamide
Polycarbonate
Dichloromethane
15 wt%
Sensor, Filter
Polylactic Acid
14 wt%
Drug Delivery System
The small size between the fibers allows the capture of particles in the 100- to nanometer range
That is the same size of viruses and bacteria
Used as air-filter: Airplanes, office, etc.
Burger, Christian, et. al. Nanofibrous Materials and Their Applications

15. Electrospinning Variables
Burger, Christian, et. al. Nanofibrous Materials and Their Applications

16. Applications
Burger, Christian, et. al. Nanofibrous Materials and Their Applications

17. Applications Ultrafiltration in water treatment
High flux, low-fouling membrane
The top layer provides the actual filtration, and the middle and bottom layer provide sting support and are very porous
Increased efficiency
Able to filter without
top layer.
Burger, Christian, et. al. Nanofibrous Materials and Their Applications
Burger, Christian, et. al. Nanofibrous Materials and Their Applications

18. Applications Anti-adhesion in surgery
Due to their high surface to volume ratio and being able to conform to different sizes, shapes and textures.
Closely match those of native tissue
Nanofabrics have been used as scaffolds for tissue and cell regeneration of organs.
Burger, Christian, et. al. Nanofibrous Materials and Their Applications
Burger, Christian, et. al. Nanofibrous Materials and Their Applications

19. Modification, crosslinking, and reactive electrospinning of a thermoplastic medical polyurethane for vascular graft applications
Recent Research on Electrospinning

20. Thermoplastic polyurethanes
Used in medical devices and experimental tissue engineering scaffolds
Chemical/mechanical properties hard to balance

21. Methodology Synthesis of a model compound
Modification of thermoplastic polyurethane
Pellethane®
Modification Reactions
Sample prep and crosslinking
Swelling behavior
Tensile testing
Scanning electron microscopy
Electrospun grafts
Synthesis of a Model
Modification
Degradation
Electrospinning
J.P. Theron et al./Acta Biomaterialia

22. Modification of Thermoplastic Polyurethane
Modified with reactive phenol groups – NaH was added - different amounts to observe changes with the polyurethane
Modified polymer was isolated and purified through precipitations in water and vacuum drying
Crosslinking achieved by UV light or heat source
Swelling index was determined by gravimetric behavior
Tensile testing was performed at room temperature and in a cyclical method
J.P. Theron et al./Acta Biomaterialia

23. Scanning electron microscopy
Surfaces of the samples – degradation study
Pellethane and Pell 15.0
Control samples (not subject to the degradation media) – used as references
Determined the amount of degradation on a scale of 1-5
J.P. Theron et al./Acta Biomaterialia

24. Electrospun grafts Small diameter vascular graft prototypes
Used an electrospinning apparatus – high voltage power supply, infusion pump, syringe, rotating/translating mandrel
Tubes removed from mandrels
by swelling in EtOH and dried
Produced crosslinked tubular vascular graft prototype
J.P. Theron et al./Acta Biomaterialia

25. Schematic Representation of the Reactive Electrospinning Apparatus
Fibers are irradiated with UV light during spinning in order to form crosslinked graft scaffolds
J.P. Theron et al./Acta Biomaterialia

26. Experimental Results
Direct linear correlation between NaH addition and degree of modification
By adding the NaH, the research group was able to get between 4.5% and 20% modification of the polyurethane.
After 20% modification, samples were discolored/started degrading
J.P. Theron et al./Acta Biomaterialia

27. Experimental Results
The range of modifications was tested for mechanical strength
The sample which ranked the best was the Pell15.0, or a 15% modified sample.
J.P. Theron et al./Acta Biomaterialia

28. Experimental Results
The modified Pell15.0 showed a reduced creep when compared to the Pellethane control – reduction of 44%
This is due to the UV crosslinking of Pell15.0.
J.P. Theron et al./Acta Biomaterialia

29. Results
Decrease in swelling index with increased degree of modification –an increased modification led to more densely crosslinked material.
Crosslinking also showed a decrease in hysteresis as well as breaking stress and strain.
The scanning electron microscope showed that the crosslinked samples had only a few cracks, while the control samples had severe surface degradation with deep cracks.
The Pell15.0 was spun with UV light into tubular graft structures 40mm in length
Grafts diameter (thickness) can be adjusted depending on specific applications
J.P. Theron et al./Acta Biomaterialia

30. Crosslinking improved the resistance to degradation.
Pellethane
Pell15.0
Before AgNO3 Degrading
After AgNO3 Degrading
After Hydrogen Peroxide
Crosslinking improved the resistance to degradation.
J.P. Theron et al./Acta Biomaterialia

31. Conclusions of this Research
Exhibit compliance values within physiological range
Can optimize fibers for mechanical, morphological properties, and in vivo response
Tissue regrowth, angiogenesis, inflammatory response
Manipulate processing conditions
Vascular grafts - repetitive, relatively low stress
Bio-degradable scaffolds for tissue regeneration
Can closely match native tissues - good incorporation in already existing tissue
J.P. Theron et al./Acta Biomaterialia

32. Surface-functionalized Elecrospun Nanofibers for Tissue Engineering and Drug Delivery
Recent Research on Electrospinning

33. Electrospun Nanofibers
High surface area to volume ratio
Versatile method for preparing nanofibrous meshes
Potential applications:
Biomedical devices
Tissue engineering scaffolds
Drug delivery carriers
Done through Surface Modification
Plasma treatment
Wet chemical method
Surface graft polymerization
Co-electrospinning of surface active agents and polymers
Creates bio-modulating microenvironments to contacting cells and tissues
"Surface-functionalized Electrospun Nanofibers for Tissue Engineering and Drug Delivery."

34. Surface Modification Techniques
Synthetic polymers vs. natural polymers
Synthetic: easier processing for electrospinning and more controllable nanofibrous morphology
Natural: difficult to directly process into nanofibers because of unstable nature and weak mechanical properties
Natural polymers can be immobilized onto the surface of synthetic polymers without compromising bulk properties
Can incorporate therapeutical
agents directly into the nanofibers
"Surface-functionalized Electrospun Nanofibers for Tissue Engineering and Drug Delivery."

35. Modification – Plasma Treatment
Changes the surface chemical composition
Selection of plasma source – introduce diverse functional groups on surface
Plasma treatments with oxygen, ammonia, or air – generates carboxyl groups or amine groups
Air or argon treatments
When nanofibers were soaked in a simulated body solution – calcium mineralization occurred on surface
Improved wettability
Potential with bone grafts
"Surface-functionalized Electrospun Nanofibers for Tissue Engineering and Drug Delivery."

36. Modification – Wet Chemical Method
Films and scaffolds under acidic or basic conditions – modify surface wettability
Plasma treatment can not modify surface of nanofibers deep in the mesh
Wet chemical etching methods can modify thick meshes
"Surface-functionalized Electrospun Nanofibers for Tissue Engineering and Drug Delivery."

37. Modification – Surface Graft Polymerization
Synthetic biodegradable polymers retain hydrophobic surface – need hydrophilic surface modification for desired response
Introduce multi-functional groups on the surface
Enhanced cell adhesion, proliferation, and differentiation
Initiated with plasma and UV radiation treatment to generate free radicals for polymerization
"Surface-functionalized Electrospun Nanofibers for Tissue Engineering and Drug Delivery."

38. Modification – Co-electrospinning
Nanoparticles and functional polymer segments can be directly exposed on surface of nanofibers
Co-electrospinning with bulk polymers
Any combination of electrospinnable polymer and polymer conjugate can be used
"Surface-functionalized Electrospun Nanofibers for Tissue Engineering and Drug Delivery."

39. Target Molecule Loading on Surface
Simple physical adsorbtion
Nanopoarticle assembly on surface
Layer by layer multilayer assembly
Chemical immobilization
"Surface-functionalized Electrospun Nanofibers for Tissue Engineering and Drug Delivery."

40. Applications – Drug Delivery
Applications – Drug Delivery
Superior adhesiveness to biological surfaces
Variety of structures containing drug molecules
Drug release mechanism – polymer degradation and diffusion pathway
Can tailor drug release profiles by varying polymer properties, surface coating, combination of polymers
Has been successful in laboratory trials – controlled topical release
"Surface-functionalized Electrospun Nanofibers for Tissue Engineering and Drug Delivery."

41. Applications – Tissue Engineering
Various cells cultivated on nanofibrous meshes
Embryonic stem cells, mesenchymal stem cells
Better than other tissue engineering methods
Coronary artery cells
Collagen
Limited to in vitro studies because cells could not be loaded within the nanofibrous meshes in large quantities
3D nanofibrous scaffolds
"Surface-functionalized Electrospun Nanofibers for Tissue Engineering and Drug Delivery."

42. Further Research

43. Improvements and Further Research
Develop more precise electrospinning techniques
Mechanisms of electrospinning
Growth rates
Bending Instability
Producing nanofabrics with specific mechanical properties.
Creating 3-dimensional shapes
Capable of being used in controlled release of drugs.
Burger, Christian, et. al. Nanofibrous Materials and Their Applications

44. Improvements and Further Research
Optimization of parameters
Intrinsic properties of solution
Polarity, surface tension of solvent,
MW of polymer, etc.
Controlling nanofiber alignment
Electric field
Modifying type of collector
Better control of fiber alignment
"Electrospin Nanofibers for Neural Tissue Engineering."

45. Improvements and Further Research
Reduce Cost of Production
Make economically viable
Increase production rate
Incorporate the use of an array of spinnerets
Safety
Solvents
Dangerous to health and environment
Polymers
Burger, Christian, et. al. Nanofibrous Materials and Their Applications

46. References
Burger, Christian, Benjamin S. Hsiao, and Benjamin Chu. "Nanofibrous Material and Their Applications." Review. 25 Apr Web. 14 Feb
Hunley, Matthew T., and Timothy E. Long. "Electrospinning Functional Nanoscale Fibers: a Perspective for the Future." Polymer International 57 (2008): Web. 7 Mar
NASA Tech Briefs Create the Future Design Contest. Web. 08 Mar < ntryID=1857>.
Theron, J. P., J. H. Knoetze, R. D. Sanderson, R. Hunter, K. Mequanint, T. Franz, P. Zilla, and D. Bezuidenhout. "Modification, Crosslinking and Reactive Electrospinning of a Thermoplastic Medical Polyurethane for Vascular Graft Applications." Acta Biomaterialia (2010). 27 Jan Web. 05 Feb
Xie, Jingwei, Matthew R. MacEwan, Andrea G. Schwartz, and Younan Xia. "Electrospin Nanofibers for Neural Tissue Engineering." Nanoscale 2 (2010): Print.
Yoo, Hyuk S., Taek G. Kim, and Tae G. Park. "Surface-functionalized Electrospun Nanofibers for Tissue Engineering and Drug Delivery." Advanced Drug Delivery Reviews 61 (2009): Print.

47. Questions

48. Rebuttal from U6
We agree that we may have used a few too many filler words and will actively try to reduce them in the second presentation
One group thought that we should have been more concise, but we felt like we had the right amount of slides to present the topic thoroughly
One group would have liked to see a more integrated presentation; we chose to add title slides throughout to let the audience know what we would be discussing next in the presentation
Potential further research was discussed in areas which showed promise in the use of nanofibers and the topics which could be researched are endless – one group suggested some additional topics to research
Polyurethane is the material which was used to produce the nanofibers, hence is how it is related to the nanotechnology applications
We will keep up the quality of the slides since there were a lot of positive comments about them
We appreciate all the comments and will take them into consideration for our next presentation

49. Review of Electrospinning of Nanofabrics
Submitted by U1

50. This presentation particularly caught our attention for its wide range of applications like clothing reinforcement and support for tissue regeneration.
Also electrospinning offers the possibility of changing some of the design and material variables to obtain different products makes it very versatile and adaptable for different purposes.
Their comparison of different papers that show electrospining base process for the aid of health issues and drug delivery shows that the technology has great future.
This presentations was really good overall and meet our expectations. The slides were well constructed and pictures were very helpful in recreating many of the concepts.

51. Electrospinning of Nanofabric
Review of Group U6’s Presentation-
Electrospinning of
Nanofabric
By Group U2:
-Kyle Demel
-Keaton Hamm
-Bryan Holekamp
-Rachael Houk

52. The presenters did really well at:
Speaking – all presenters in this group were easy to hear and understand
Outlining the presentation and going in a logical and easy-to-follow order
Giving a thorough introduction
Maintaining consistency in text size/fonts
Using big and helpful graphics
Discussing the articles in detail
Other future applications to discuss:
Clothing that repels germs, dirt, allergens
Clothing with microelectronic nano-generators to produce energy
Incorporating microelectronics with three-dimensional tissue engineering
Video-imaging on skin
Adding nanofabrics to buildings

53. Electrospinning of Nanofabrics
Group 3:
Krista Melish James Kancewick
Phillip Keller Mike Jones

54. Presentation Review: Ugrad #6
Material Review
Effective job communicating the material
I have never heard of electrospinning before, and I was able to follow along and understand what was being presented easily
Need to reduce use of verbal distractors (umm, like, etc.) and pauses
Always a need to reduce these, but overall the material was communicated clearly
Some pictures seemed unnecessary
Pictures are nice to have but just including them to fill space (such as on the second further improvements slide) should be limited
Instead, condense several points onto a single page
Overall Grade: 95
The introduction was concise, yet effective in explaining basic concepts that the research paper looked at further.
The graphics used to depict size, demonstrate procedure, and present results were utilized very effectively within the presentation.
For example, the process of electrospinning was shown very clearly in your report through the use of several figures. Effective visual format for the material.
Questions for further research:
Very specific, showing deep thought and breadth of knowledge
Good detail in specifying which aspects of electrospinning should receive further attention
Good insight considering the safety of the materials used and generated, this subject is generally neglected.

55. Electrospinning of Nanofabrics
Review by Group U4
Burger, Christian, et. al. Nanofibrous Materials and Their Applications

56. Review of Oral presentation and Slides
Both presenters were audible from the back of the room
Confidence was lacking in the second presenter, sentences were repeated multiple times
Presenters, when not presenting should still look engaged not bored staring into space
Slides
It seemed like information could have been more concise, but it was split up to make the presentation look longer.
Pictures on pages were not always related to the information discussed.
Everything was well cited
Graphs and tables were easy to read and understand

57. Technical Content
All aspects of electrospinning were described in detail.
Research against the subject seemed lacking, and what was done didn’t seem to have a rebutal.
Further research was very in depth, present a second paper on the medial uses of electrospinning
Very informative, but further research is needed to determine, among others, if it will affect the consumer in a negative way.
Burger, Christian, et. al. Nanofibrous Materials and Their Applications

58. Review of Electrospinning of Nanofabrics
Review of Group U6 by Group U5 58

59. Oral and Quality of Slides
Speakers had very good oral presentation skills. Clear, confident, and knowledgeable in their discussion.
Font size and pictures were appropriately sized and well cited.

60. Technical Review
Very sound technical report. Appeared to have extensive and relevant research.
Would have liked to see a more integrated presentation, instead of segmented by paper titles.

61. Review for U6
Jung Hwan Woo

62. I didn’t clearly understand how the thermoplastic polyeurethane is related to the nanotechnology. Is this material a type of “nanofibers” described earlier in the presentation? The connection between these will help improve the presentation.
How is the homogeneity achieved during the co-electrospinning? Is this something that must be controlled? Does it have an impact on the final product?