ELECTROSPINNING OF NANOFIBERS

NANOFIBERS

With dimension of 100 nanometers (nm) or less (National Science Foundation, India)

As defined by the Non – woven industry, nanofiber is any fiber that has a diameter of less than 1 micron (<1000 nm) (Hegde, R.R. et al, 2005).

NANOFIBERS

Figure 1. Comparison between human hair and nanofiber web [1].

NANOFIBERS

Figure 2. Entrapped pollen spore on nanofiber web [1].

NANOFIBERS

Figure 3. Comparison of red blood cell with nanofibers web [1].

NANOFIBERS

Figure 4. Ultra – Web® Nanofiber Filter Media used commercially. (taken from Grafe, 2003)

First nanofibers produced in the Material Science Lab, IMSP, UPLB

Figure 5. Polycaprolactone nanofiber (a) and (b) has fiber diameters between 273 nm to 547 nm. SEM taken with 10,000X magnification.(J.I.Zerrudo, E.A.Florido, 2008)

First nanofibers produced in the Material Science Lab, IMSP, UPLB

Figure 6. 75:25 Polycaprolactone(PCL)/Polyethylene Oxide (PEO) blend nano 10,000X magnification.(J.I.Zerrudo, E.A.Florido, SPP Physics Congress, October 2008)

First nanofibers produced in the Material Science Lab, IMSP, UPLB

Figure 7. SEM Micrograph of Poly(DL-lactide-co-glycolide) nanofibersWith diameter range of 59nm-126 nm.(J.Clarito, E.A.Florido, October 2008)

First nanofibers produced in the Material Science Lab, IMSP, UPLB

Figure 8. SEM Micrograph of Poly(DL-lactide-co-glycolide) nanofiberswith diameters of 86 nm, 194 nm, 201 nm.(J.Clarito, E.A.Florido, October 2008)

First nanofibers produced in the Material Science Lab, IMSP, UPLB

Figure 9. SEM Micrograph of Poly(DL-lactide-co-glycolide) nanofibermesh.(J.Clarito, E.A.Florido, October 2008)

First nanofibers produced in the Material Science Lab, IMSP, UPLB

Figure 10. SEM Micrograph of Polyvinyl chloride nanofiber with at least 76 nm diameter. (J.Garcia, E.A.Florido, February 2009)

First nanofibers produced in the Material Science Lab, IMSP, UPLB

Figure 11. 22 nm-diameter polyvinyl chloride nanofiber with a porous microfiber in the background. (J.Garcia, E.A.Florido, February 2009)

Applications of Nanofibers

Material Reinforcements and filters (BHOWMICK, S. A. Et al. 2006)

Tissue and Organ Implants (RAMAKRISHNA, S.M., et al. 2004)

Extra Cellular Matrix (QUEEN, 2006)

Cosmetics- Higher utilization- Higher transfer rate

Drug delivery- Increased dissolution rate- Drug-nanofiber interlace

Electrical conductors- Ultra small devices

Filter media- Higher filter efficiency

Haemostatic devices- Higher efficiency in fluid

absorption

Wound dressing- Prevents scar- Bacterial shielding

Protective clothing- Breathable fabric that

blocks chemicals

Optical applications- Liquid crystal optical shutters

Sensor devices- Higher sensitivity- For cells, arteries and veins

Material reinforcement- Higher fracture toughness- Higher delamination resistance

Tissue engineering scaffolds- Adjustable biodegradation rate- Better cell attachment- Controllable cell directional growth

Medical prostheses- Lower stress concentration- Higher fracture strength

Polymer Nanofiber

Ramakrishna et al. 2004

ELECTROSPINNINGUses high voltage to draw very fine fibers

(micro- or nano-scale) from a liquid (soloution or melt).

The high voltage produces an electrically charged jet of polymer solution or melt, which dries or solidifies leaving a polymer fiber

the process was patented in 1934 by Formhals [2-4]

ELECTROSPINNING

Figure 12. Schematic of Electrospinning Process Courtesy: www.che.vt.edu

ELECTROSPINNING

Figure 13 The distribution of charge in the fiberchanges as the fiber dries out during flight

Figure 14. Electrospinning set-up in the IMSP Physics Division Materials Science Laboratory. J.I.Zerrudo, E.A. Florido

Taylor Cone refers to the cone observed in electrospinning,

electrospraying and hydrodynamic spray processes from which a jet of charged particles emanates above a threshold voltage

was described by Sir Geoffrey Ingram Taylor in 1964 before electrospray was "discovered“

to form a perfect cone required a semi-vertical angle of 49.3° (a whole angle of 98.6°) , the shape of such a cone approached the theoretical shape just before jet formation – Taylor Angle

Taylor Cone

• Taylor angle. This angle is more precisely where is the first zero of (the Legendre polynomial of order 1/2).

two assumptions: (1) that the surface of the cone is an

equipotential surface and (2) that the cone exists in a steady state

equilibrium

Taylor ConePotential

Equipotential surface

The zero of the Legendre polynomial between 0 and piis 130.70990 which is the complement (supplement)of the Taylor angle.

Taylor Cone

• When a sufficiently high voltage is applied to a liquid droplet, the body of the liquid becomes charged, and electrostatic repulsion counteracts the surface tension and droplet is stretched, at a critical point a stream of liquid erupts from the surface. This point of eruption is known as the Taylor cone

NANOFIBRES T. A. Kowalewski, A. L. Yarin & S.

Błoński, EFMC 2003, Toulouse

Classical liquid jet

Orifice – 0.1mm

Primary jet diameter ~ 0.2mm

0.1mm

Micro-jet diameter ~ 0.005mm

Gravitational, mechanical or electrostatic pulling limited to l/d ~ 1000 by capillary instabilityTo reach nano-range:

jet thinning ~10-3 draw ratio ~106 !

Taylor Cone.

J.T.Garcia, E.A. Florido

NANOFIBRES T. A. Kowalewski, A. L. Yarin & S. Błoński, EFMC 2003,

Toulouse

Electrospinning

E ~ 105V/m

v=0.1m/s

moving charges e bending force on charge e

viscoelastic and surface tension resistance

Moving charges (ions) interacting with electrostatic field amplify bending instability, surface tension and viscoelasticity counteract these forces

NANOFIBRES T. A. Kowalewski, A. L. Yarin & S. Błoński, EFMC 2003, Toulouse

Electro-spinningSimple model for elongating viscoelastic thread

Non-dimensional length of the thread as a function of electrostatic potential

Stress balance: - viscosity, G – elastic modulus stress, stress tensor, dl/dt – thread elongation

Momentum balance: Vo – voltage, e – charge, a – thread radius, h- distance pipette-collector

Kinematic condition for thread velocity v

NANOFIBRES T. A. Kowalewski, A. L. Yarin & S. Błoński, EFMC 2003, Toulouse

Electro-spinning

E ~ 105V/m

Bending instability enormously increases path of the jet, allowing to solve problem: how to decrease jet diameter 1000 times or more without increasing distance to tenths of kilometres

bending instability of electro-spun jet

charges moving along spiralling path

Parameters

1. Molecular Weight, Molecular-Weight Distribution and Architecture (branched, linear etc.) of the polymer

2. Solution properties (viscosity, conductivity & and surface tension)

3. Electric potential, Flow rate & Concentration4. Distance between the capillary and collection screen5. Ambient parameters (temperature, humidity and air

velocity in the chamber)6. Motion of target screen (collector)

Figure 14. Electrospinning set-up in the IMSP Physics Division Materials Science Laboratory. J.I.Zerrudo, E.A. Florido

Fibers produced during electrospinning.

J.I.Zerrudo, E.A. Florido

Fibers produced during electrospinning.

J.I.Zerrudo, E.A. Florido

PVC Fibers produced during electrospinning.

J.T.Garcia, E.A. Florido

PVC Fibers produced during electrospinning.

J.T.Garcia, E.A. Florido

A.O.Advincula, E.A. Florido

J.C. La Rosa, E.A. Florido

Electrospinning in MatPhy Lab, IMSP, UPLB

1. PEO microfibers, Jennette Rabo, Maricon R. Amada, 2006

2. Polyaniline and Polyaniline/Polyester microfibers, Jefferson D. Diego, M.R.Amda, Emmanuel A. Florido, 2006

3. Polycaprolactone/Polyethylene Oxide nanofibers, Juzzel Ian Zerrudo, Emmanuel A. Florid0, 2008

4. Polycaprolactone (pcl)/Polyethylene oxide (peo)/iota carrageenan (ιcar) blends, Serafin M. Lago III, Teoderick Barry R. Manguerra, 2008.

Electrospinning in MatPhy Lab, IMSP, UPLB

4. Poly (DL-lactide-co-glycolide)(85:15) PLGA and PLGA/Polycaprolactone (PCL) nanofibers, Christian Joseph Clarito, Emmanuel A. Florido, 2008

5. Polyvinyl Chloride (PVC) nanofibers from scrap PVC pipes, Ben Jairus T. Garcia, 2009

Nanoresearch in UPLB: Physics Division, Institute of Mathematical Sciences and Physics, CAS

• K.S.A. Revelar. An Investigation on the Morphological and Antimicrobial Properties of Electrospun Silver Nanoparticle-Functionalized Polyvinyl Chloride Nanofiber Membranes. IMSP, UPLB. April 2010. Undergraduate Thesis, Adviser: EAFlorido. Co-Adviser: R.B.Opulencia

• A.O.Advincula. Effect of varying Areas of Parallel Plates on Fiber Diameter of Electrospun Polyvinyl Chloride. IMSP, UPLB. April 2010. Undergraduate Thesis, Adviser: EAFlorido

• H.P.Halili. Effect of Solution Viscosity and Needle Diameter on Fiber Diameter of Electrospun Polycaprolactone. IMSP, UPLB. October 2010. Undergraduate Thesis, Adviser: EAFlorido. Co-Adviser: J.I.B. Zerrudo

• J.C.M. La Rosa. Effects of Variation of Distance Between Needle Tip and Collector On the Fabrication of Polyaniline (PANI)-Polyvinyl Chloride (PVC) Blend Nanofibers. IMSP, UPLB. April 2009. Undergraduate Thesis, Co-Adviser: EAFlorido

• M.J.P.Gamboa. The Effects of Viscosity on the Morphological Characteristics of Electrospun Polyaniline-Polyvinyl Acetate (PAni-PVAc) Nanofibers. IMSP, UPLB. April 2009. Undergraduate Thesis, Co-Adviser: EAFlorido

• J.I.B. Zerrudo, E.A. Florido, M.R. Amada, Fabrication of Polycaprolactone Nanofibers through Electrospinning, Proceedings of the Samahang Pisika ng Pilipinas, ISSN 1656-2666, vol. 5,October 22-24, 2008.

• J.I.B. Zerrudo, E.A. Florido, M.R. Amada, B.A.Basilia, Fabrication of Polycaprolactone/Polyehtylene Oxide Nanofibers through Electrospinning, Proceedings of the Samahang Pisika ng Pilipinas, ISSN 1656-2666, vol. 5,October 22-24, 2008.

• B.J.Garcia. Morphological and Molecular Characterization of Electrospun Polyvinyl chloride-Polyaniline Nanofibers. IMSP, UPLB. April 2009. Undergraduate Thesis, Adviser: EAFlorido

• J.D. Diego. Electrospinning of Polyaniline and Polyaniline/Polyester Based Fibers. IMSP, UPLB. November 2006.Undergraduate Thesis, Adviser: EAFlorido