NEEDLELESS ELECTROSPINNING OF NANOFIBERS Pan Stanford Series on Renewable Energy — Volume 2 Tong Lin Xungai Wang NEEDLELESS ELECTROSPINNING OF NANOFIBERS Technology and Applications editors Preben Maegaard Anna Krenz Wolfgang Palz The Rise of Modern Wind Energy Wind Power for the World CRC Press Taylor & Francis Group 6000 Broken Sound Parkway NW, Suite 300 Boca Raton, FL 33487-2742 © 2013 by Taylor & Francis Group, LLC CRC Press is an imprint of Taylor & Francis Group, an Informa business No claim to original U.S. Government works Version Date: 20131021 International Standard Book Number-13: 978-981-4316-84-2 (eBook - PDF) This book contains information obtained from authentic and highly regarded sources. Reason- able efforts have been made to publish reliable data and information, but the author and publisher cannot assume responsibility for the validity of all materials or the consequences of their use. 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CCC is a not-for-profit organiza- tion that provides licenses and registration for a variety of users. For organizations that have been granted a photocopy license by the CCC, a separate system of payment has been arranged. Trademark Notice: Product or corporate names may be trademarks or registered trademarks, and are used only for identification and explanation without intent to infringe. Visit the Taylor & Francis Web site at http://www.taylorandfrancis.com and the CRC Press Web site at http://www.crcpress.com Contents Preface Acknowledgments ix 1. Introduction to Electrospinning x1i 1.1 Electrospinning 1 1.1.1 Brief History 2 1.1.2 Electrospinning Process and Principles 3 1.1.3 Fiber Morphology 10 1.2 Characteristics of Electrospun Nanofibers 12 1.3 Improved Electrospinning Techniques 13 2. 1Em.4e rginFgi bAeprp-lCicoalltieocntisn ogf M Eloedcetrso spun Nanofibers 1273 2.1 Biomedical 23 2.1.1 Tissue Engineering Scaffolds 23 2.1.2 Blood Vessels 24 2.1.3 Bones 27 2.1.4 Cartilages 29 2.1.5 Muscles 30 2.1.6 Skins 31 2.1.7 Neural Tissues 32 2.1.8 Other Tissue Scaffolds 34 2.1.9 Wound Healing 34 2.1.10 Drug Delivery and Release Control 37 2.2 Environmental Protection 39 2.2.1 Filtration 39 2.2.2 Metal Ion Adsorption and Recovery 41 2.3 Catalyst and Enzyme Carriers 43 2.3.1 Catalysts 43 2.3.2 Enzymes 45 2.4 Sensors 46 2.5 Energy Harvest and Storage 49 2.5.1 Solar Cells 49 2.5.2 Fuel Cells 51 vi Contents 2.5.3 Mechanical Energy Harvesters 52 2.5.4 Lithium Ion Batteries 53 2.5.5 Supercapacitors 56 2.5.6 Hydrogen Storage 57 3. 2D.e6v elopOmthenerts A inp pLlaicrgaeti-oSncasl e Nanofiber 58 Electrospinning Systems 61 3.1 Downward Multi-Jet Electrospinning 61 3.2 Upward Needleless Electrospinning 66 4. Upward 3N.2e.e1d lelEelsesc Etrleocstprionsnpiinngn iTnegc whnitihq uDeissc , Ball, 66 and Cylinder Spinnerets 71 4.1 Cylinder Electrospinning 71 4.1.1 Effects of Applied Voltage and PVA Concentration 72 4.1.2 Effect of Cylinder End Shape 74 4.1.3 Effect of Cylinder Diameter 75 4.2 Ball Electrospinning 76 4.3 Disc Electrospinning 77 4.3.1 Effects of Applied Voltage and PVA Concentration 78 4.3.2 Effect of Disc Thickness 80 5. Upward 4N.3e.e3d lelCeosms Eplearcitsroonsp inning with Ring 81 and Coil Spinnerets 83 5.1 Ring Electrospinning 83 5.1.1 Single Ring 83 5.1.2 Multiple-Ring Spinnerets 86 5.2 Wire Coil Electrospinning 87 5.2.1 Conical Coil Electrospinning 87 5.3 Effects of Experimental Parameters on Fiber Quality 89 5.3.1 PVA Concentration 89 5.3.2 Applied Voltage 90 5.3.3 Collecting Distance 91 5.4 Tubular Wire Coil Electrospinning 92 5.4.1 Spinning Process 93 5.4.2 Parameters Affecting Fiber Morphology 94 Contents vii 5.5 Effects of Coil Shape on Needleless Electrospinning 95 5.5.1 Spinneret Length 95 5.5.2 Spiral Distance 96 5.5.3 Coil Diameter 97 5.5.4 Wire Diameter of the Coil 98 5.6 Effects of Experimental Parameters 98 5.6.1 Coil Rotating Speed 98 5.6.1.1 Applied voltage 98 5.6.2 Collecting Distance 99 5.6.3 PVA Concentration 100 5.7 Comparison 100 5.7.1 Needle and Coil Electrospinning 100 5.7.2 Multiple Rings and Coils 104 6. Electrica5l .F7i.e3l d ACnoamlypsiasr isons of Different Nozzles 110059 6.1 Cylinder Electrospinning 111 6.2 Ball Electrospinning 115 6.3 Disc Electrospinning 117 6.4 Shaft-Linked Multiple Discs 121 6.5 Ring Electrospinning 123 6.6 Multiple Rings 129 6.7 Conical Wire Coil Electrospinning 130 6.8 Tubular Wire Coil 131 6.9 Comparison of Cylinder, Disc, Ring, and Coil 132 7. 6Fi.b1e0r CoClloelcltiecotno rs 113357 7.1 Effect of Collector Shape 137 7.2 Effect of Collection Media 139 7.3 Effect of Collecting Distance 140 8. 7Co.4n clusiEoffne acnt do fO Auitrl oFolokw 141 Index 187 Preface Electrospun nanofibers have shown enormous application potential in diverse areas. However, most works on electrospinning nanofibers are based on conventional needle electrospinning techniques, and mass production of nanofibers for practical applications has been a great challenge with the needle electrospinning systems. This book systemically introduces a relatively new electrospinning process, needleless electrospinning. The book is divided into seven chapters. In the first chapter, basic electrospinning theory is introduced. The second chapter summarizes the functional applications of electrospun nanofibers in different fields. Chapter 3 reviews the emerging electrospinning technologies that have potential for large-scale production of nanofibers. Chapters 4 and 5 describe an important needleless electrospinning technique using different fiber generators such as ball, cylinder, disc, and wire coil, and the effects of the fiber generator, its shape and dimension, and operating parameters on electrospinning performance, fiber morphology, and productivity are also introduced. Chapter 6 analyzes the electric field profiles and provides a method to calculate the electric field intensity in an electrospinning zone. Chapter 7 discusses the influence of the fiber collector on fiber quality. The book will be a very useful resource for academics, industry professionals, and graduate students in nanomaterials, nanostructures, and nanofabrication .