ELECTRO SPINNING FOR NANO FIBRES

1. ELECTRO SPINNING FOR NANO FIBRES

2. Group Members • A.A.T.N.Athauda • H.H.S. Chamara • S.M. Abeyweera • A.C. Darshana • M. Amalan

3. INTRODUCTION • This presentation basically gives about how the nano fiber can be manufactured using Electro spinning process and their readily available applications. • Especially about the carbon nano tubes and the polymeric nano fiber structures are discussed along with the nano structure applications.

4. What is “Nano” ? • "The science of small" is truly an interdisciplinary science, in which material scientist, biologists, chemists and Physics share knowledge to extend the Nano-scale boundaries. One billionth of a meter (l0-9 m) about 80,000 times smaller than a human hair • The nano-scale also marks the grey zone where classical laws and quantum - mechanical laws meet each other.

5. Nano Fiber • Nano fibers are defined as fibers with diameters on the order of 100 nanometers. • Nano fibers have fiber diameters of nanometer (nm) scales that are 5~10 times smaller than smallest melt blown fiber available (AFD <500nm) • Nano fibers have several amazing characteristics, such as very large surface area to volume ratio (~1000 m2/g).

6. Nano fiber Diameter Comparison

7. Nano Fiber Contd… • They can be produced by • Interfacial polymerization • Drawing • Template Synthesis • Phase Separation • Self-Assembly • Electro spinning

8. Interfacial Polymerization • Interfacial polymerization is an alternative to bulk polymerization of condensation polymers which would require high temperatures. • Two immiscible solvents are used, with monomer in one solvent reacting with monomer in the other solvent. • Higher molecular weights are obtained because monomer is more likely to encounter a growing chain than the opposing monomer See Figure

9. Interfacial Polymerization Contd…

10. Drawing • The drawing is a process similar to dry spinning in fiber industry, which can make one-by-one very long single nano fibers. • However, only a visco-elastic material that can undergo strong deformations while being cohesive enough to support the stresses developed during pulling can be made into nano fibers through drawing.

11. Template Synthesis • The template synthesis, uses a nano porous membrane as a template to make nano fibers of solid (a fibril) or hollow (a tubule) shape. • The most important feature of this method may lie in that nanometer tubules and fibrils of various raw materials such as electronically conducting polymers, metals, semiconductors, and carbons can be fabricated. • On the other hand, the method cannot make one-by-one continuous nano fibers.

12. Phase Separation • The phase separation consists of dissolution, gelation, extraction using a different solvent, freezing, and drying resulting in a nano scale porous foam. • The process takes relatively long period of time to transfer the solid polymer into the nano-porous foam.

13. Self Assembly • The self-assembly is a process in which individual, pre-existing components organize themselves into desired patterns and functions. • However, similarly to the phase separation the self-assembly is time-consuming in processing continuous polymer nano fibers.

14. Electro Spinning • Electro spinning is the process of using electrostatic forces to distort a pendant droplet of polymer solution into a fine filament to be deposited onto a substrate. • Electro spinning shares characteristics of both Electro Spaying (Electro hydrodynamic Atomization) and conventional solution dry spinningof fibers.

15. Comparison between existing production method

16. But …..

17. Electro Spinning • Electro spinning is the process of using electrostatic forces to distort a pendant droplet of polymer solution into a fine filament to be deposited onto a substrate. • Electro spinning shares characteristics of both Electro Spaying (Electro hydrodynamic Atomization) and conventional solution dry spinningof fibers.

18. Electro Spinning Process

19. Photograph of a fiber being electro spun from a Taylor cone.

20. Electro Spinning Process in detail • Electrospinning is one of the basic methods for producing fibres with nanometric diameters. • It relies on electrostatic forces to produce fibers in the nanometer scale. • Under the influence of the electrostatic field, a pendant droplet of the polymer solution at the spinneret is deformed into a conical shape. • If the voltage surpasses a threshold value, electrostatic forces overcome the surface tension and a fine charged jet is ejected. See Figure

21. Photograph of a fiber being electro spun from a Taylor cone

22. Electro Spinning Process in detail • As these electric forces increase, the jet will elongate, accelerate by the electric forces and the solvent evaporates. • Splaying occurs in a region in which the radical forces from the electrical charges carried by the jet, become larger than the cohesive forces within the jet, and the single jet divides into many fibers and deposits on a substrate as a random nano fiber mat. See Figure

23. Splaying Effect When a strong electrostatic force is applied to the capillary containing a polymer solution, the solution is ejected from the capillary and deposited as a nonwoven fibrous mat on a template serving as the ground for electric charges

24. Electro Spinning Process in detail..

25. Electro Spinning Apparatus Basic four components • High voltage DC power supply • Metallic spinneret or pipette • Positive displacement syringe pump • Collector plate

26. Realistic View

27. Characteristics of Electro Spun Nano Fibers • Very large surface area to volume ratio (this ratio for a Nano fiber can be as large as 103 times of that of a microfiber) • High porosity • Ultra-thin and light weight material • Membrane-like textile • Possibility of mixture with other • Soft touch • Superior mechanical performance (stiffness and tensile strength)

28. Nano Fiber Alignment in Electro spinning process • A cylinder collector with high rotating speed • An auxiliary electrode • An auxiliary electrical field • A thin wheel with sharp edge • A frame collector • Oscillating a grounded multi frame collector • Multiple field technique

29. Cylinder Collector method • Electro spun nano fibers could be oriented circumferentially. • Fiber alignment Speed Cylinder Rotation Speed ~ ~

30. Electrode Collection process The auxiliary electrode (grid) made of a plurality of connected aluminum foil strips in 5 mm width, 30 mm long, and 5 mm apart, was placed 8 cm away from the collection mandrel and charged to -8 kV

31. Electrical field Collecting Process Electro spun ultrafine fibers with larger diameter

32. Thin wheel with Sharp edge process Before reaching the electrically grounded target the nano fibers retain sufficient residual charges to repel each other. Once a nano fiber is attached to the wheel tip, it exerts a repulsive force on the next fiber attracted to the tip. This repulsion from one another results in a separation.

33. Other approaches Frame Collector Multi Frame Collector

34. Other approaches Contd… Control the deposition of electro spun polymer nano fibers and even collects nicely aligned fiber yarns.

35. Advantages of Electro Spinning • Ability to produce novel synthetic fibers of unusually small diameter and good mechanical properties. • This leads to fiber mats with high surface area to volume ratio and the ability to control pore size. • Potential applications for nanometer-diameter polymer filaments including separation membranes, wound dressing materials, artificial organs, nano-composites, and protective clothing

36. Advantages of Electro Spinning contd.. • It provides three important advantages over other solvent spinning methods. • Solvent cost will be cancelled. • Does not include any toxic content hence being Environmental friendly. • Solventcan be thought as loss for productivity. Polymer melt will completely electrospun, but solvent will evaporate during solution based electrospinning. • No need to prepare solution for thermoplastic fibres.

37. Drawbacks in Electro Spinning • Viscosity is one of the basic parameters of electrospinning. Polymer melts generally have higher viscosity values than solutions. • Heat insulation is compulsory for holding viscosity smaller • For melting the polymer, metallic ion parts must be used. That causes electrical discharges more frequently. Many scientists changed polarity to overcome that problem. By changing polarity productivity will decrease and nanofiber diameter will increase

38. Drawbacks in Electro Spinning Contd… • Formation of beads • Thick place in a nano fibre • Act as a disadvantage when it comes a to the alignment • When the viscosity is decreased, the surface tension of the solution is increased, then the inter molecular forces is increased hence forming thick places in the fibre. Beads

39. Drawbacks in Electro Spinning Contd… • Uneven cross section of the fiber surface with pore structure • At high temperature, the porosity is less due to the reduction of viscosity in the solution

40. Applications of Electro Spun Nano Fibers • Military protective clothing • Life seeking applications • Cosmetic applications • Biomedical applications • Structural elements in artificial organs • Nano-composites • Filtering applications • Porous membrane • Nano sensors

41. Tissue Engineering • Porous membrane skin • Tubular shapes for blood vessels and nerves • 3D Scaffolds for bone regenerations • Military Protective Clothing • Anti Bio Chemical gases • Minimal impedance to air • Efficiency in trapping aerosol particles • Nano Sensors • Thermal sensor • Piezoelectric sensor • Biochemical sensor • Cosmetic Skin Mask • Skin Healing • Skin Cleansing • Skin therapy Polymer Nano Fiber • Filter Media • Liquid Filtration • Gas Filtration • Molecular Filtration • Other Applications • Micro electronic devices • Electrostatic Dissipation • Electromagnetic shielding • Application in Life Seeking • Drug delivery carrier • Wound Dressing • Haemostatic devices

42. Application - Tissue Engineering At day 1, the cells were elongated At day 3, there was an increase in cell densities across cell types compared to day 1 At day 7, the cells increase in their numbers significantly and almost reach confluence on the nano fiber mesh

43. Application – Porous Membrane

44. Application Contd… Bio molecular vascular Substitute Wound Dressing

45. Application Statistics Reference - www.elsevier.com/locate/compscitech

46. Application –Material Types • Nylon • Nylon 4,6 as nano fiber reinforcement • Textile Composites • Acetate • Antimicrobial ultrafine cellulose • PE • Poly ethylene Glycol • Antimicrobial ultrafine cellulose • Poly ethylene oxide [PEO] • Carbon Nano tubes • Viscose

47. Limitations of using Nano fibres in textiles • Polymer specific production. Unable to cover overall applications in textiles due to this. • Low production speeds collaborates with higher production cost. • Unable to produce a continuous fiber (only fiber webs in tiny lengths) • Too fragile to be handled

48. New developments in Nano Fibres • Continuous fiber yarn made out of electro spun nano fibers (Suit for Textiles) • 75m/min production rate (viable in industry) • Ease of forming nano fiber made out of different polymer mixtures • • Ability to mix different fibers composed of different polymer • Functionalizing of electro spun fiber is possible • Fabrication of ceramic nano fiber through secondary processes

49. Specific Applications in Nano Fibres Carbon Nano Tubes

50. What is a Nano Tube ?? • Tube with 100nm of inner diameter and 200nm of outer diameter • Having high modulus and tensile strength • Has several walls to surround the inner tubes made by poly ethylene oxide [PEO] • Diameters are controlled by using an inner liquor (Mineral Oil) 100nm 200nm