Electrospinning: Not just for DJs anymore… Kendra A. Erk Advisor: Dr. Jeffrey P. Youngblood REU Final Presentation August 5, 2004

Presentation Outline Introduction to electrospinning and conducting polymers Electrospinning observations and results Resistance and resistivity analysis Summary and future work

Electrospinning Basics Process by which high static voltages are used to produce fibers from a polymer solution Micron to submicron diameter Fibers have huge SA:Volume ratio Applications: filters, wound dressing, composite reinforcement

ES Process Polymer solution with sufficient viscosity High voltages applied to solution Fibers deposit on collection target Rutledge Group, MIT

ES Apparatus

Conducting Polymers “synthetic metals” which combine chemical and mechanical properties of polymers with electronic properties of metals Easy and inexpensive to make, flexible, light-weight, and stable Replace metals used in some applications like molecular wires in nanostructures

Polymers v. Metals N.J. Pinto

My Research Direction Original Project Goals: Electrospin conducting fibers from water- soluble conducting polymers or conducting/structural polymer blends Electrospin conducting fibers from water- soluble conducting polymers or conducting/structural polymer blends Polyaniline sulfonic acid, 5 wt% in water (PAS) Polyvinyl alcohol (PVA) Examine the effect of polymer blending on spinning parameters and conductivity Examine the effect of polymer blending on spinning parameters and conductivity

Conducting Polymer: PAS Early Spinning: Spun conducting polymer as purchased Spun conducting polymer as purchased Sufficient viscosity Sufficient viscosity Result: spray, fibrous chunks Result: spray, fibrous chunks 5 wt% polyaniline sulfonic acid in water

Structural Polymer: PVA Poly(vinyl alcohol) Soluble in water Soluble in water Semicrystalline Semicrystalline Chemically and thermally stable Chemically and thermally stable Highly biocompatible, nontoxic Highly biocompatible, nontoxic Ribbon fibers formed at low PVA concentrations 1.04 wt% PVA in water, kV at 26 cm

Structural Polymer: PVA Optimal concentration ~ 7.45 wt% PVA in water Result: smooth fibers, d ~ 0.6 – 3 microns 5.36 wt% PVA, kV, 26.5 cm7.43 wt% PVA, kV, 26 cm

Polymer Blends: PAS & PVA PAS:PVA  1:0.5 to 1:4 in 0.5 PVA increments Results: visible fibers, brown/yellow in color, micron diameters, best spun by drops 1:4 PAS:PVA 1:1.5 PAS:PVA

Polymer Blends: PAS & PVA Best spinning from 1:1-1:2.5 At low PVA conc. fibers bridge to frame, high fiber yield At high PVA conc. fibers mat to slide, low fiber yield 1:3.5 1:1.5

Resistance Analysis of PAS/PVA Blends MPJA 9903 Autoranging Multimeter (max 30 MΩ) 1x1 cm thin films Electrospun fibers

Summary Water-soluble conducting polymer PAS blended with PVA was successfully electrospun PAS/PVA: high yield, smooth, micron fibers For resistance testing, thin films and fibers were produced from the various PAS/PVA blend ratios: Resistivity increased with increasing PVA concentrations Resistivity increased with increasing PVA concentrations Solutions with PVA < 67 wt% produce fibers and films more conducting than silicon, a semiconductor Solutions with PVA < 67 wt% produce fibers and films more conducting than silicon, a semiconductor

Future Work Try other structural polymers Refine electrospinning techniques (capillary pump, charged box) Isolate specific fibers and use SEM to determine more accurate diameters and cross-sectional areas Photovoltaic applications

Acknowledgements Dr. Youngblood and the Y-team: Ben Eick, John Howarter, Phil Sellenet, Allen Mackey, Alicia Certain Ben Eick, John Howarter, Phil Sellenet, Allen Mackey, Alicia Certain Dr. Kvam and Dr. Trice Fellow REU students NSF

Questions?