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).

Figure 1. Comparison between human hair and nanofiber web [1]. 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) nanofibers With 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) nanofibers with 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) nanofiber mesh. (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)‏

Ramakrishna et al. 2004 Polymer Nanofiber Tissue engineering scaffolds - Adjustable biodegradation rate - Better cell attachment - Controllable cell directional growth Wound dressing - Prevents scar - Bacterial shielding Medical prostheses - Lower stress concentration - Higher fracture strength Haemostatic devices - Higher efficiency in fluid absorption Drug delivery - Increased dissolution rate - Drug-nanofiber interlace Polymer Nanofiber Sensor devices - Higher sensitivity - For cells, arteries and veins Cosmetics - Higher utilization - Higher transfer rate Filter media - Higher filter efficiency Electrical conductors - Ultra small devices Protective clothing Breathable fabric that blocks chemicals Material reinforcement - Higher fracture toughness - Higher delamination resistance Optical applications Liquid crystal optical shutters Ramakrishna et al. 2004

ELECTROSPINNING Uses 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 fiber changes 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: that the surface of the cone is an equipotential surface and (2) that the cone exists in a steady state equilibrium

Taylor Cone Potential Equipotential surface The zero of the Legendre polynomial between 0 and pi is 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

Classical liquid jet  0.1mm  Orifice – 0.1mm Primary jet diameter ~ 0.2mm Micro-jet diameter ~ 0.005mm Gravitational, mechanical or electrostatic pulling limited to l/d ~ 1000 by capillary instability To reach nano-range: jet thinning ~10-3 draw ratio ~106 ! NANOFIBRES T. A. Kowalewski, A. L. Yarin & S. Błoński, EFMC 2003, Toulouse

Taylor Cone. J.T.Garcia, E.A. Florido

Electrospinning v=0.1m/s E ~ 105V/m 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

Simple model for elongating viscoelastic thread Electro-spinning Simple model for elongating viscoelastic thread 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 Non-dimensional length of the thread as a function of electrostatic potential NANOFIBRES T. A. Kowalewski, A. L. Yarin & S. Błoński, EFMC 2003, Toulouse

Electro-spinning bending instability of electro-spun jet E ~ 105V/m charges moving along spiralling path 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 NANOFIBRES T. A. Kowalewski, A. L. Yarin & S. Błoński, EFMC 2003, Toulouse

Parameters Molecular Weight, Molecular-Weight Distribution and Architecture (branched, linear etc.) of the polymer Solution properties (viscosity, conductivity & and surface tension) Electric potential, Flow rate & Concentration Distance between the capillary and collection screen Ambient parameters (temperature, humidity and air velocity in the chamber) 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 PEO microfibers, Jennette Rabo, Maricon R. Amada, 2006 Polyaniline and Polyaniline/Polyester microfibers, Jefferson D. Diego, M.R.Amda, Emmanuel A. Florido, 2006 Polycaprolactone/Polyethylene Oxide nanofibers, Juzzel Ian Zerrudo, Emmanuel A. Florid0, 2008 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 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