Electrospinning Principles, Practice and Possibilities RSC Polymer Chemistry Series Editor-in-Chief: Professor Ben Zhong Tang, The Hong Kong University of Science and Technology, Hong Kong, China Series Editors: Professor Alaa S. Abd-El-Aziz, University of Prince Edward Island, Canada Professor Stephen Craig, Duke University, USA Professor Jianhua Dong, National Natural Science Foundation of China, China Professor Toshio Masuda, Shanghai University, China Professor Christoph Weder, University of Fribourg, Switzerland Titles in the Series: 1: Renewable Resources for Functional Polymers and Biomaterials 2: Molecular Design and Applications of Photofunctional Polymers and Materials 3: Functional Polymers for Nanomedicine 4: Fundamentals of Controlled/Living Radical Polymerization 5: Healable Polymer Systems 6: Thiol-X Chemistries in Polymer and Materials Science 7: Natural Rubber Materials: Volume 1: Blends and IPNs 8: Natural Rubber Materials: Volume 2: Composites and Nanocomposites 9: Conjugated Polymers: A Practical Guide to Synthesis 10: Polymeric Materials with Antimicrobial Activity: From Synthesis to Applications 11: Phosphorus-Based Polymers: From Synthesis to Applications 12: Poly(lactic acid) Science and Technology: Processing, Properties, Additives and Applications 13: Cationic Polymers in Regenerative Medicine 14: Electrospinning: Principles, Practice and Possibilities How to obtain future titles on publication: Astandingorderplanisavailableforthisseries.Astandingorderwillbring delivery of each new volume immediately on publication. For further information please contact: BookSalesDepartment,RoyalSocietyofChemistry,ThomasGrahamHouse, Science Park, Milton Road, Cambridge, CB4 0WF, UK Telephone: þ44 (0)1223 420066, Fax: þ44 (0)1223 420247 Email: [email protected] Visit our website at www.rsc.org/books Electrospinning Principles, Practice and Possibilities Edited by Geoffrey R. Mitchell Centre for Rapid and Sustainable Product Development, Institute Polytechnic of Leiria, Marinha Grande, Portugal Email: geoff[email protected] RSCPolymerChemistrySeriesNo.14 PrintISBN:978-1-84973-556-8 PDFeISBN:978-1-84973-557-5 ISSN:2044-0790 AcataloguerecordforthisbookisavailablefromtheBritishLibrary rTheRoyalSocietyofChemistry2015 Allrightsreserved Apartfromfairdealingforthepurposesofresearchfornon-commercialpurposesor forprivatestudy,criticismorreview,aspermittedundertheCopyright,Designsand PatentsAct1988andtheCopyrightandRelatedRightsRegulations2003,thispublication maynotbereproduced,storedortransmitted,inanyformorbyanymeans,without thepriorpermissioninwritingofTheRoyalSocietyofChemistry,orinthecaseof reproductioninaccordancewiththetermsoflicencesissuedbytheCopyrightLicensing AgencyintheUK,orinaccordancewiththetermsofthelicencesissuedbytheappropriate ReproductionRightsOrganizationoutsidetheUK.Enquiriesconcerningreproduction outsidethetermsstatedhereshouldbesenttoTheRoyalSocietyofChemistryatthe addressprintedonthispage. TheRSCisnotresponsibleforindividualopinionsexpressedinthiswork. Theauthorshavesoughttolocateownersofallreproducedmaterialnotintheirown possessionandtrustthatnocopyrightshavebeeninadvertentlyinfringed. PublishedbyTheRoyalSocietyofChemistry, ThomasGrahamHouse,SciencePark,MiltonRoad, CambridgeCB40WF,UK RegisteredCharityNumber207890 Forfurtherinformationseeourwebsiteatwww.rsc.org Preface Electrospinning is an emerging manufacturing technology which parallels the current drive towards multidisciplinary science, involving an exciting mix of engineering, physical chemistry and physics, together with science from a breadth of applications, extending from regenerative medicine to energy harvesting, wound dressings to catalysts, and synthetic meat to high performance composites. Much of electrospinning is associated with polymers and the infinite variety of polymers mixes well with the variation and control available through electrospinning to prepare materials and structures for diverse requirements. This book arose out of a conference series organised by the Institute of Physics in London with the support of the Dielectrics Group, the Polymer PhysicsGroupandtheElectrostaticsGroup.Thefirstinthisserieswasheld in 2010 and the third in December 2013. The vast majority of the authors presentedtheirworkatthesemeetings.Iammostgratefulfortheirpositive response to turning these efforts into a book chapter. I have set out to provide a book that I would have found useful when Istartedworkonelectrospinningandwouldbeveryinterestedtoreadtoday. We start the book with an introduction to electrospinning which, coupled with Chapter 2, a glossary of terms, provides a great overview to electro- spinning and electrospun fibres for those new to the field. Hopefully, the glossaryoftermswillprovideacommonlanguageforelectrospinnerstouse to describe their work. The history of electrospinning from a commercial exploitation perspective, prepared by Nick Tucker, provides a fascinating insight into an idea looking for applications. It should be noted in this regardthatthescanningelectronmicroscope,theprincipaltoolforimaging electrospun fibres, was not developed until the 1950s, with commercial instruments only coming on stream in the 1960s. RSCPolymerChemistrySeriesNo.14 Electrospinning:Principles,PracticeandPossibilities EditedbyGeoffreyR.Mitchell rTheRoyalSocietyofChemistry2015 PublishedbytheRoyalSocietyofChemistry,www.rsc.org v vi Preface Chapter 4 takes us through the process parameters for optimising the electrospinning process and in Chapter 5 Greenfield and Zussman discuss the connections between the microscopic behaviour in the electrospinning jet and the physics of the jet. This is followed by two chapters from the pioneersintheirrespectivefields,namelymeltelectrospinningandcolloidal electrospinning. These chapters are then followed by one addressing the developmentofstructure,bothintermsofexternalandinternalmorphology during electrospinning. Guy Schattler shows how we can build complex structures usingelectrospinning and Asa Barber describes the properties of electro-spun nanofibres. Chapter 11 highlights many of the opportunities that electrospun fibres provide in medicine and biomedical devices and Chapter 12 focuses on the use of electrospun scaffolds to grow synthetic meat.Thebookconcludeswiththatmostdifficultoftasks,gaugingwhatwill happen in the future. With some certainty, we can say that in light of the versatility of electrospinning techniques, there is ample scope for many surprises over the next ten years. Geoffrey Mitchell Marinha Grande, Portugal Contents Chapter 1 Introduction 1 Fred J. Davis, Saeed D. Mohan and Muaathe A. Ibraheem 1.1 Polymer Fibres 1 1.2 Principles of Electrospinning 3 1.3 Equipment for Electrospinning 4 1.4 Processing Parameters 7 1.5 Materials 11 1.6 Characterisation of Fibres 14 1.7 Health and Safety 16 1.8 Applications 17 1.9 Summary 18 References 18 Chapter 2 Glossary of Terms 22 Jonathan Stanger and Fred J. Davis Chapter 3 The Development of Electrospinning Technologies for Commercial Application 34 Nick Tucker 3.1 Introduction 34 3.2 John Francis Cooley 39 3.3 William James Morton 42 3.4 Kiyohiko Hagiwara 42 3.5 Anton Formhals 43 3.6 Charles Ladd Norton 46 3.7 Petryanov Filters 47 3.8 Fred W Manning 48 RSCPolymerChemistrySeriesNo.14 Electrospinning:Principles,PracticeandPossibilities EditedbyGeoffreyR.Mitchell rTheRoyalSocietyofChemistry2015 PublishedbytheRoyalSocietyofChemistry,www.rsc.org vii viii Contents 3.9 1944–1970 USA 48 3.10 1976–1987 Europe 50 3.11 Current Times 1990s 53 Acknowledgements 53 References 54 Chapter 4 Optimising Solutions for Electrospinning 57 Stuart R. Coles and Andrew Wooldridge 4.1 Introduction 57 4.2 Feedstock Properties 58 4.2.1 Solution Concentration 59 4.2.2 Molecular Weight and Surface Tension 60 4.2.3 Conductivity 62 4.3 Experimental Setup 62 4.3.1 Flow Rate 62 4.3.2 Electric Field Strength 63 4.3.3 Grounded Collector Design 64 4.3.4 Fibre Collection Methodology 64 4.4 Environmental Conditions 66 4.4.1 Temperature 66 4.4.2 Humidity 67 4.5 Conclusion 69 References 69 Chapter 5 Polymer Network Dynamics during Electrospinning: Random Walk Simulation 71 Israel Greenfeld and Eyal Zussman 5.1 Introduction 71 5.2 Random Walk Simulation of Polymer Chains 72 5.2.1 Background 72 5.2.2 Theoretical Basis 75 5.3 Single Chain 76 5.3.1 Chain under Tension 76 5.3.2 Free Chain in a Flow Field 79 5.4 Network in a Flow Field 82 5.4.1 Polymer System and Forces 82 5.4.2 Network Dynamics 86 5.4.3 Analytic Approximation 89 5.5 Discussion and Conclusions 90 5.6 Appendix: Random Walk Simulation Tool 93 5.6.1 Program and Examples 93 5.6.2 Network Simulation Procedure 96 Acknowledgements 97 References 97 Contents ix Chapter 6 Design and Fabrication of Scaffolds via Melt Electrospinning for Applications in Tissue Engineering 100 Paul D. Dalton, M. Lourdes Muerza-Cascante and Dietmar W. Hutmacher 6.1 Background 100 6.2 Scaffold Design and Fabrication 101 6.3 The Melt Electrospinning Process 102 6.4 Fibre Homogeneity and Uniformity 105 6.5 Melt Electrospinning Configurations 105 6.5.1 Heating Systems 106 6.5.2 Applied Voltage 107 6.5.3 Collection Distance 107 6.5.4 Spinneret Diameter 108 6.5.5 Temperature 108 6.5.6 Flow Rate 108 6.5.7 Collector Type 108 6.6 Melt Electrospinning Writing 109 6.7 3D Architectures and Structures for TE Scaffolds 110 6.8 Applications of Melt Electrospun Scaffolds in Tumour and Tissue Engineering Applications 111 6.9 Conclusion 115 Acknowledgements 116 References 116 Chapter 7 Electrospinning of Nanoparticles 121 Daniel Crespy 7.1 Introduction 121 7.2 Principles and Preparation Procedures 122 7.2.1 Principles 122 7.2.2 AggregationStateoftheNanoparticlesinthe Feed and in the Fibres 123 7.2.3 Morphologies of the Fibres and of the Colloids in the Fibres 123 7.3 Relevant Characterization Techniques 128 7.3.1 AggregationStateoftheNanoparticlesinthe Electrospinning Feed 128 7.3.2 AggregationStateoftheNanoparticlesinthe Fibres 128 7.4 Selected Applications of Colloid-electrospinning 129 7.4.1 Catalysis,EnergyProductionandConversion 129 7.4.2 Antiwetting 132 7.5 Biomedical Applications 132 7.6 Conclusions and Perspectives 132 References 133 x Contents Chapter 8 Structure Development in Electrospun Fibres 136 Geoffrey R. Mitchell, Saeed D. Mohan, Fred J. Davis, Kyung-Hwa Ahn, Mohamed Al-Azab, Ahmed El Hadi, Delyth Elliott, Mahadevappa Y. Kariduraganavar, Anitha Nagarajan and Meruyert Nazhipkyzy 8.1 Introduction 136 8.2 Structure Development Transferred from Solution 137 8.2.1 Polymers in Solution 137 8.2.2 Cluster Formation in PEO-based Aqueous Solutions 141 8.2.3 Hydrogen Bonding 142 8.3 Structure Development During Electrospinning 143 8.3.1 Use of a Rotating Collector 143 8.3.2 Porosity 148 8.3.3 State of the Fibre at Solidification 150 8.3.4 Shape of Fibre 152 8.3.5 Nanophase Separation in Block Copolymers 155 8.3.6 Electrospun Nanocomposites 156 8.3.7 Chain Trajectories 156 8.3.8 Blends and Additives 159 8.3.9 Semicrystalline Polymers 162 8.3.10 Temperature 166 8.4 Structure Development Post Electrospinning 166 8.4.1 Residual Solvent 166 8.4.2 Structural Transformation Using Solvent Vapour Treatment 166 8.4.3 Cross-linking 168 8.4.4 Other Chemical Reactions 168 8.5 Summary 169 Acknowledgements 169 References 169 Chapter 9 Organized Assembly of Electrospun Nanofibres: From 1D to 3D 172 Salima Nedjari, Anne H´ebraud and Guy Schlatter 9.1 Fibre Alignment 173 9.1.1 Electrostatic Forces 173 9.1.2 Magnetic Forces 177 9.1.3 Mechanical Forces 178 9.2 2D Patterned Nanofibrous Membranes 181 9.2.1 2D Composites Formed from 1D Aligned Fibres 181