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

Electrospinning of Nanofabrics

Presented by U6:Pavitra TimbaliaMichael TrevathanJared Walker

Outline

•Introduction•Background

Apparatus General Applications

•Current Research•Future Research•Questions

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. 2006.

http://en.wikipedia.org/wiki/File:Taylor_cone_photo.jpg

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” junctionsBurger, Christian, et. al. Nanofibrous Materials and Their Applications. 2006.

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


Electrospinning

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 ejectedBurger, Christian, et. al. Nanofibrous Materials and Their Applications.

2006.





Types of Solvent Stream Ejections


20 wt%

Poly(D,L-lactic acid) (PDLA) Nanofibers at voltage of 20 kV, feeding rate of 20 μl min−1


Poly(D,L-lactic acid) (PDLA) Nanofibers at voltage of 20 kV, feeding rate of 20 μl min−1

35 wt%

Electrospinning Polymers

•The small size between the fibers allows the capture of particles in the 100- to 300- 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. 2006.

Polymer Solvent ConcentrationPotential

ApplicationNylon 6,6 Formic Acid 10 wt% Protective Clothing

PolyurethanesDimethylformamid

e 10 wt% Protective Clothing

Polycarbonate Dichloromethane 15 wt% Sensor, Filter

Polylactic Acid Dichloromethane 14 wt%Drug Delivery

System

Electrospinning Variables


Applications


ApplicationsUltrafiltration 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.



ApplicationsAnti-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.

2006.


Modification, crosslinking, and reactive electrospinning of a thermoplastic medical polyurethane for vascular graft applicationsRecent Research on Electrospinning

Thermoplastic polyurethanes

• Used in medical devices and experimental tissue engineering scaffolds

• Chemical/mechanical properties hard to balance

http://www.perfectex.com/tpu01.jpg

http://www.allproducts.com/manufacture100/tpu/product1.jpg

http://www.pslc.ws/macrog/images/ureth06.gif

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

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

http://upload.wikimedia.org/wikipedia/commons/2/25/Sodium-hydride-3D-vdW.png


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

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 prototypeJ.P. Theron et al./Acta Biomaterialia

Schematic Representation of the Reactive Electrospinning Apparatus


• Fibers are irradiated with UV light during spinning in order to form crosslinked graft scaffolds

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



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.


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.

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



• Crosslinking improved the resistance to degradation.

Pellethane Pell15.0

Before AgNO3 Degrading

After AgNO3 Degrading

After Hydrogen Peroxide

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

http://hairyinterfaces.memphys.sdu.dk/DMueller_fig1.jpg


Surface-functionalized Elecrospun Nanofibers for Tissue Engineering and Drug DeliveryRecent Research on Electrospinning

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."

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


http://www.animate4.com/nanotech/nanotechnology/nanomedicine/nano/nanoscale/nanotech-nanotechnology-nano-nanomedicine-moleculare-nanotech-nanoscale.jpg

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


http://www.devicedaily.com/wp-content/uploads/2008/11/fortross-02.jpg

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


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


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


Target Molecule Loading on Surface

•Simple physical adsorbtion•Nanopoarticle assembly on surface•Layer by layer multilayer assembly•Chemical immobilization


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."

http://www.keystonenano.com/library/images/moleculeAsmall.jpg

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."

http://pcsl.mit.edu/images/nano.jpg

Further Research

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. 2006.


•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."

http://www.rsc.org/ejga/NR/2010/b9nr00243j-ga.gif


•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


References• Burger, Christian, Benjamin S. Hsiao, and Benjamin Chu. "Nanofibrous

Material and Their Applications." Review. 25 Apr. 2006. Web. 14 Feb. 2010. • Hunley, Matthew T., and Timothy E. Long. "Electrospinning Functional

Nanoscale Fibers: a Perspective for the Future." Polymer International 57 (2008): 385-89. Web. 7 Mar. 2010.

• NASA Tech Briefs Create the Future Design Contest. Web. 08 Mar. 2010. <http://www.createthefuturecontest.com/pages/view/entriesdetail.html?entryID=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. 2010. Web. 05 Feb. 2010.

• Xie, Jingwei, Matthew R. MacEwan, Andrea G. Schwartz, and Younan Xia. "Electrospin Nanofibers for Neural Tissue Engineering." Nanoscale 2 (2010): 35-44. 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): 1033-042. Print.

Questions

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

Review of Electrospinning of Nanofabrics

Submitted by U1

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.

http://www3.interscience.wiley.com/journal/118859172/issue

http://realitypod.com/?tag=artificial

By Group U2: -Kyle Demel

-Keaton Hamm

-Bryan Holekamp

-Rachael Houk

http://www.power.uwaterloo.ca/HVEL/images/Previewtheretical_mod.jpg

Review of Group U6’s Presentation-

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

http://i.ytimg.com/vi/bt-lv6IJPxc/0.jpg

http://www.treehugger.com/files/2008/05/nano-vent-skin.php

http://gtresearchnews.gatech.edu/newsrelease/power-shirt.htm

Group 3: Krista Melish James

KancewickPhillip Keller Mike Jones


Presentation Review: Ugrad #6Presentation Review 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.


Review by Group U4


Review of Oral presentation and Slides

• Oral Presentation– 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

http://www.animate4.com/nanotech/nanotechnology/nanomedicine/nano/nanoscale/nanotech-nanotechnology-nano-nanomedicine-moleculare-nanotech-nanoscale.jpg

Technical Content

Very informative, but further research is needed to determine, among others, if it will affect the consumer in a negative way.

– 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


Review of Group U6 by Group U5

Review of Electrospinning of Nanofabrics

Oral and Quality of SlidesSpeakers had very

good oral presentation skills. Clear, confident, and knowledgeable in their discussion.

Font size and pictures were appropriately sized and well cited.

Technical ReviewVery 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.

Review for U6

Jung Hwan Woo

• 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?

Documents

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