Electrospinning: Nanofabrication and Applications

Electrospinning: Nanofabrication and Applications presents an overview of the electrospinning technique, nanofabrication strategies and potential applications. The book begins with an introduction to the fundamentals of electrospinning, discussing fundamental principles of the electrospinning process, controlling parameters, materials and structures. Nanofabrication strategies, including coaxial electrospinning, multi-needle electrospinning, needleless electrospinning, electro-netting, near-field electrospinning, and three-dimensional macrostructure assembling are also covered. Final sections explore the applications of electrospun nanofibers in different fields and future prospects. This is a valuable reference for engineers and materials scientist working with fibrous materials and textiles, as well as researchers in the areas of nanotechnology, electrospinning, nanofibers and textiles.

• Explores controllable fabrication of electrospun nanomaterials and their multifunctional applications
• Explains the electrospinning technique as used in nanofabrication and nanofibers
• Outlines the applications of electrospun nanofibrous materials in tissue engineering, filtration, oil-water separation, water treatment, food technology, supercapacitors, sensors and so on

• Language: English
• Publisher: Elsevier Science
• Release date: Nov 12, 2018
• ISBN: 9780128134412

Book preview

Electrospinning

Nanofabrication and Applications

Editors

Bin Ding

Innovation Center for Textile Science and Technology, Donghua University, Shanghai, China

Xianfeng Wang

Key Laboratory of Textile Science & Technology, Ministry of Education, College of Textiles, Donghua University, Shanghai, China

Innovation Center for Textile Science and Technology, Donghua University, Shanghai, China

Jianyong Yu

Innovation Center for Textile Science and Technology, Donghua University, Shanghai, China

Table of Contents

Cover image

Title page

Copyright

Contributors

Part 1. Fundamentals of Electrospinning

Chapter 1. Introduction and Historical Overview

1.1. Introduction

1.2. Electrospinning

1.3. Nanofibers: Solving Global Issues

1.4. Outlook

Chapter 2. Electrospinning: The Setup and Procedure

2.1. Basic Electrospinning Setup and Procedure

2.2. Modification of Electrospinning Setup: Collector

2.3. Modification of Electrospinning Setup: Spinneret

2.4. Portable Electrospinning Setup

2.5. Industrial Electrospinning Setups

Chapter 3. Nanofibrous Materials

3.1. Electrospun Polymeric Nanofibers

3.2. Electrospun Inorganic Nanofibers

3.3. Electrospun Polymer/Inorganic Composite Nanofibers

3.4. Conclusions

Chapter 4. Nanofibrous Structures

4.1. Introduction

4.2. Nano over Micro, Meso, and Macro

4.3. Production Methods of Nanofibrous Structures

4.4. Utility of Nanofibrous Structures

Part 2. Nanofabrication Strategies From Electrospinning

Chapter 5. Coaxial Electrospinning

5.1. Introduction

5.2. The Structures of Various Fibers

5.3. Applications of Coelectrospun Fibers

5.4. Conclusion and Future Perspective

Chapter 6. Multineedle Electrospinning

6.1. Introduction to the Multineedle Electrospinning System

6.2. Multineedle Electrospinning Modes

6.3. Large-Scale Multineedle Electrospinning

6.4. Diversified Product Forms of Multineedle Electrospinning

6.5. Conclusion

Chapter 7. Needle-less Electrospinning

7.1. Introduction

7.2. Needle-less Electrospinning With Motionless Spinnerets

7.3. Needle-less Electrospinning with Moving Spinnerets

7.4. Needle-less Electrospinning Enhanced by External Force Fields

7.5. Needle-less Electrospinning Technique Disclosed in Patents

7.6. Needle-less Electrospinning Machines

7.7. Issues Associated with Needle-less Electrospinning

7.8. Summary

Chapter 8. Electronetting

8.1. Introduction

8.2. Electronetting Nanotechnology

8.3. Nanofiber/Nanonet Membranes

8.4. Effects of Various Parameters on Electronetting

8.5. Application of Nanofiber/Nanonet Membranes

8.6. Concluding Remarks and Perspectives

Chapter 9. Near-Field Electrospinning

9.1. Introduction

9.2. Mechanism and Jet Behavior of Near-Field Electrospinning

9.3. Electrohydrodynamic Direct Writing Based on Near-Field Electrospinning

9.4. Electrohydrodynamic Direct-Write Micro/Nanostructures

9.5. Applications of Near-Field Electrospinning

9.6. Summary and Future Work

Chapter 10. Centrifugal Spinning—High Rate Production of Nanofibers

10.1. Introduction

10.2. A Brief History of Centrifugal Spinning

10.3. Fiber Formation

10.4. Centrifugal Spinning System

10.5. Types of Materials for Centrifugal Spinning

10.6. Effect of Processing Parameters on Centrifugally Spun Fiber Structure

10.7. Application of Centrifugal Spinning Products

10.8. Electrocentrifugal Spinning

10.9. Summary

Chapter 11. Melt Electrospinning

11.1. Introduction

11.2. Historical Perspective

11.3. Principles of Melt Electrospinning

11.4. Process Research and Fiber Diameter

11.5. Configurations of Melt Electrospinning Setups

11.6. Industrial Potential Applications of Melt Electrospinning

11.7. Conclusions and Future Perspectives

Part 3. Applications of Electrospun Nanofibers

Chapter 12. Electrospun Nanofibers for Air Filtration

12.1. Introduction

12.2. Electrospun Nanofiber Filters

12.3. Polymeric Nanofiber-Based Filters

12.4. Hybrid Nanofiber-Based Filters

12.5. Nanofiber/Net-Based Filters

12.6. Inorganic Nanofiber-Based Filters

12.7. Concluding Remarks and Perspectives

Chapter 13. Electrospun Nanofibers for Oil–Water Separation

13.1. Introduction

13.2. Electrospun Nanofibrous Absorbents for Oil-Spill Cleanup

13.3. Electrospun Nanofibrous Filter Membranes for Oil–Water Separation

13.4. Electrospun Nanofibrous Aerogels for Oil–Water Separation

13.5. Conclusions and Future Perspectives

Chapter 14. Electrospun Nanofibers for Water Treatment

14.1. Introduction

14.2. Nanofiber Membranes

14.3. Nanofiber-Based Composite Membranes

14.4. Conclusions

Chapter 15. Electrospun Nanofibers for Food and Food Packaging Technology

15.1. Introduction

15.2. Electrospinning of Biopolymeric Nanofibers in the Food Industry

15.3. Electrospinning of Synthetic Polymeric Nanofibers in the Food Industry

15.4. Functionalization of Nanofibers

15.5. Application in Food Packaging Technology

15.6. Conclusions and Perspectives

Chapter 16. Electrospun Nanofibers for Protein Adsorption

16.1. Introduction

16.2. Fabrication and Bioseparation Studies of Adsorptive Membranes and Felts Made From Electrospun Cellulose Acetate Nanofibers

16.3. Surface-Functionalized Electrospun Carbon Nanofiber Mats as an Innovative Type of Protein Adsorption or Purification Medium With High Capacity and High Throughput

Chapter 17. Electrospun Nanofibers for Waterproof and Breathable Clothing

17.1. Introduction

17.2. Electrospun Nanofibers for Waterproof and Breathable Clothing

17.3. Conclusion and Future Trends

Chapter 18. Electrospun Nanofibers for Sensors

18.1. Introduction

18.2. How to Design Electrospun NM–Based Sensing Materials

18.3. Electrochemical Sensors

18.4. Optical Sensors

18.5. Resistive Sensors

18.6. Mass-Change-Sensitive Sensors (Quartz Crystal Microbalance Sensors)

18.7. Summary and Perspectives

Chapter 19. Electrospun Nanofibers for Optical Applications

19.1. Optical Properties of Pristine Electrospun Nanofibers and the Corresponding Optical Applications

19.2. Optical Properties of Doped Electrospun Nanofibers and the Corresponding Optical Applications

19.3. Optical Applications of Electrospun Nanofibers with Further Treatment

19.4. Summary

Chapter 20. Electrospun Nanofibers for Carbon Dioxide Capture

20.1. Introduction

20.2. Traditional Materials for CO2 Capture

20.3. Key Issues of Porous Materials

20.4. Electrospun Nanofibers for CO2 Capture

20.5. Concluding Remarks and Outlook

Chapter 21. Electrospun Nanofiber Electrodes: A Promising Platform for Supercapacitor Applications

21.1. Introduction

21.2. Electrospun Electrochemical Double-Layer Capacitive Nanomaterials for Supercapacitors

21.3. Electrospun Pseudocapacitive Nanomaterials for Supercapacitors

21.4. Electrospun Nanofiber-Based Composite Electrodes for Supercapacitors

21.5. Conclusions and Outlook

Chapter 22. Electrospun Nanofibers for Lithium-Ion Batteries

22.1. Introduction to Lithium-Ion Batteries

22.2. Electrospun Nanofiber Anodes

22.3. Electrospun Nanofiber Cathodes

22.4. Electrospun Nanofiber Separators

22.5. Conclusions and Outlook

Chapter 23. Electrospun Nanofibers for Catalysts

23.1. Introduction

23.2. Methods for Preparing Nanofibrous Catalysts

23.3. Electrospun Nanofibers as Catalysts

23.4. Catalysts Supported on Electrospun Nanofibers

23.5. Conclusions

Chapter 24. Electrospun Nanofibers for Tissue Engineering

24.1. Introduction

24.2. Electrospun Nanofibers for Tendon Tissue Engineering Applications

24.3. Electrospun Nanofibers for Vascular Tissue Engineering Applications

24.4. Electrospun Nanofibers for Nerve Tissue Engineering Applications

24.5. Conclusion

Chapter 25. Electrospun Nanofibers for Drug Delivery

25.1. Introduction

25.2. Approaches to Incorporating Drugs for Release

25.3. Types of Drugs for Release

25.4. Medical Applications of Drug-Eluting Fiber Matrices

25.5. Future Perspectives

25.6. Conclusion

Chapter 26. Electrospun Nanofibers for Enzyme Immobilization

26.1. Introduction

26.2. Enzyme Immobilization Strategies for Electrospun Nanofibers

26.3. Application Fields of Enzymes Immobilized by Electrospun Nanofibers

26.4. Summary and Perspectives

Index

Copyright

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Contributors

Mohammed Awad Abedalwafa

Key Laboratory of Textile Science and Technology, Ministry of Education, College of Textiles, Donghua University, Shanghai, PR China

Department of Technical Textile, Faculty of Industries Engineering and Technology, University of Gezira, Wad Madani, Sudan

Seema Agarwal,     University of Bayreuth, Macromolecular Chemistry and Bavarian Polymer Institute, Bayreuth, Germany

Aijaz Ahmed Babar

Key Laboratory of Textile Science & Technology, Ministry of Education, College of Textiles, Donghua University, Shanghai, China

State Key Laboratory for Modification of Chemical Fibers and Polymer Materials, College of Materials Science and Engineering, Donghua University, Shanghai, China

Innovation Center for Textile Science and Technology, Donghua University, Shanghai, China

Chen Chen,     Fiber and Polymer Science Program, Department of Textile Engineering, Chemistry and Science, North Carolina State University, Raleigh, NC, United States

Xiaoqing Chen,     College of Mechanical and Electrical Engineering, Beijing University of Chemical Technology, Beijing, China

Cheng Cheng,     State Key Laboratory for Modification of Chemical Fibers and Polymer Materials, Donghua University, Shanghai, People's Republic of China

Jun Cheng,     Department of Chemistry and Chemical Biology, Stevens Institute of Technology, Hoboken, NJ, United States

Hongbing Deng,     Hubei International Scientific and Technological Cooperation Base of Sustainable Resource and Energy, Hubei Key Lab of Biomass Resource Chemistry and Environmental Biotechnology, School of Resource and Environmental Science, Wuhan University, Wuhan, P. R. China

Bin Ding,     Innovation Center for Textile Science and Technology, Donghua University, Shanghai, China

Mahmut Dirican,     Fiber and Polymer Science Program, Department of Textile Engineering, Chemistry and Science, North Carolina State University, Raleigh, NC, United States

Xiangyang Dong,     Hubei International Scientific and Technological Cooperation Base of Sustainable Resource and Energy, Hubei Key Lab of Biomass Resource Chemistry and Environmental Biotechnology, School of Resource and Environmental Science, Wuhan University, Wuhan, P. R. China

Hao Fong,     Department of Chemistry and Applied Biological Sciences, South Dakota School of Mines and Technology, Rapid City, SD, United States

Qiuxia Fu,     Key Laboratory of Textile Science and Technology, Ministry of Education, College of Textiles, Donghua University, Shanghai, China

Jianlong Ge,     Key Laboratory of Textile Science and Technology, Ministry of Education, College of Textiles, Donghua University, Shanghai, China

Andreas Greiner,     University of Bayreuth, Macromolecular Chemistry and Bavarian Polymer Institute, Bayreuth, Germany

Jianxin He,     Provincial Key Laboratory of Functional Textile Materials, Zhongyuan University of Technology, Zhengzhou, China

Jianchen Hu,     National Engineering Laboratory for Modern Silk, College of Textile and Clothing Engineering, Soochow University, Suzhou, Jiangsu, PR China

Fenglin Huang,     Key Laboratory of Eco-Textiles, Ministry of Education, Jiangnan University, Wuxi, Jiangsu, China

Mengtian Huang,     Hubei International Scientific and Technological Cooperation Base of Sustainable Resource and Energy, Hubei Key Lab of Biomass Resource Chemistry and Environmental Biotechnology, School of Resource and Environmental Science, Wuhan University, Wuhan, P. R. China

Nousheen Iqbal

State Key Laboratory for Modification of Chemical Fibers and Polymer Materials, College of Materials Science and Engineering, Donghua University, Shanghai, China

Key Laboratory of Textile Science & Technology, Ministry of Education, College of Textiles, Donghua University, Shanghai, China

Jiaxin Jiang,     Department of Instrumental and Electrical Engineering, Xiamen University, Xiamen, China

Shaohua Jiang,     College of Materials Science and Engineering, Nanjing Forestry University, Nanjing, China

Dandan Li,     State Key Lab for Modification of Chemical Fibers & Polymer Materials, College of Chemistry, Chemical Engineering and Biotechnology, Donghua University, Shanghai, China

Dawei Li,     Key Laboratory of Eco-Textiles, Ministry of Education, Jiangnan University, Wuxi, Jiangsu, China

De Li,     Key Laboratory of Textile Science and Technology, Ministry of Education, College of Textiles, Donghua University, Shanghai, PR China

Haoyi Li

College of Mechanical and Electrical Engineering, Beijing University of Chemical Technology, Beijing, China

State Key Laboratory of Organic-Inorganic Composites, Beijing, China

Lei Li,     College of Biological, Chemical Sciences and Engineering, Jiaxing University, Jiaxing, China

Xiong Li,     State Key Laboratory for Modification of Chemical Fibers and Polymer Materials, Donghua University, Shanghai, People's Republic of China

Yan Li,     Key Laboratory of Textile Science and Technology, Ministry of Education, College of Textiles, Donghua University, Shanghai, PR China

Tong Lin,     Institute for Frontier Materials, Deakin University, Geelong, Victoria, Australia

Haiqing Liu,     College of Biological, Chemical Sciences and Engineering, Jiaxing University, Jiaxing, China

Hui Liu

Key Laboratory of Textile Science & Technology, Ministry of Education, College of Textiles, Donghua University, Shanghai, China

Innovation Center for Textile Science and Technology, Donghua University, Shanghai, China

Lifang Liu,     Key Laboratory of Textile Science & Technology, Ministry of Education, College of Textiles, Donghua University, Shanghai, China

Rong Liu,     Hubei International Scientific and Technological Cooperation Base of Sustainable Resource and Energy, Hubei Key Lab of Biomass Resource Chemistry and Environmental Biotechnology, School of Resource and Environmental Science, Wuhan University, Wuhan, P. R. China

Tianxi Liu,     State Key Laboratory for Modification of Chemical Fibers and Polymer Materials, College of Materials Science and Engineering, Innovation Center for Textile Science and Technology, Donghua University, Shanghai, PR China

Yun-Ze Long

Collaborative Innovation Center for Nanomaterials & Devices, College of Physics, Qingdao University, Qingdao, China

Industrial Research Institute of Nonwovens & Technical Textiles, Qingdao University, Qingdao, China

Ping Lu,     Department of Chemistry and Biochemistry, Long Island University, Brooklyn, NY, United States

Xiaofeng Lu,     Alan G. MacDiarmid Institute, College of Chemistry, Jilin University, Changchun, PR China

Todd J. Menkhaus,     Department of Chemical and Biological Engineering, South Dakota School of Mines and Technology, Rapid City, SD, United States

Yue-E Miao,     State Key Laboratory for Modification of Chemical Fibers and Polymer Materials, College of Materials Science and Engineering, Innovation Center for Textile Science and Technology, Donghua University, Shanghai, PR China

Xiumei Mo,     State Key Lab for Modification of Chemical Fibers & Polymer Materials, College of Chemistry, Chemical Engineering and Biotechnology, Donghua University, Shanghai, China

Simone Murray,     Department of Chemistry and Biochemistry, Long Island University, Brooklyn, NY, United States

Haitao Niu,     Institute for Frontier Materials, Deakin University, Geelong, Victoria, Australia

Deep Parikh,     Department of Biomedical Engineering, Stevens Institute of Technology, Hoboken, NJ, United States

Nadir Ali Rind

Key Laboratory of Textile Science & Technology, Ministry of Education, College of Textiles, Donghua University, Shanghai, China

Innovation Center for Textile Science and Technology, Donghua University, Shanghai, China

Junlu Sheng,     Key Laboratory of Textile Science & Technology, Ministry of Education, College of Textiles, Donghua University, Shanghai, China

Mary Stack,     Department of Biomedical Engineering, Stevens Institute of Technology, Hoboken, NJ, United States

Binbin Sun,     State Key Lab for Modification of Chemical Fibers & Polymer Materials, College of Chemistry, Chemical Engineering and Biotechnology, Donghua University, Shanghai, China

Daoheng Sun,     Department of Mechanical and Electrical Engineering, Xiamen University, Xiamen, China

Liqin Tang,     Key Laboratory of Textile Science and Technology, Ministry of Education, College of Textiles, Donghua University, Shanghai, PR China

Ning Tang

Key Laboratory of Textile Science & Technology, Ministry of Education, College of Textiles, Donghua University, Shanghai, China

Innovation Center for Textile Science and Technology, Donghua University, Shanghai, China

Jing Tian

College of Food Science and Technology and MOE Key Laboratory of Environment Correlative Dietology, Huazhong Agricultural University, Wuhan, P. R. China

Hubei International Scientific and Technological Cooperation Base of Sustainable Resource and Energy, Hubei Key Lab of Biomass Resource Chemistry and Environmental Biotechnology, School of Resource and Environmental Science, Wuhan University, Wuhan, P. R. China

Ce Wang,     Alan G. MacDiarmid Institute, College of Chemistry, Jilin University, Changchun, PR China

Haoyu Wang,     Department of Chemistry and Chemical Biology, Stevens Institute of Technology, Hoboken, NJ, United States

Hongjun Wang

Department of Biomedical Engineering, Stevens Institute of Technology, Hoboken, NJ, United States

Department of Chemistry and Chemical Biology, Stevens Institute of Technology, Hoboken, NJ, United States

Lichen Wang,     Department of Biomedical Engineering, Stevens Institute of Technology, Hoboken, NJ, United States

Lu Wang,     Key Laboratory of Textile Science and Technology, Ministry of Education, College of Textiles, Donghua University, Shanghai, PR China

Min Wang,     State Key Laboratory for Modification of Chemical Fibers and Polymer Materials, Donghua University, Shanghai, People's Republic of China

Nü Wang,     Key Laboratory of Bioinspired Smart Interfacial Science and Technology of Ministry of Education, Beijing Key Laboratory of Bioinspired Energy Materials and Devices, School of Chemistry, Beijing Advanced Innovation Center for Biomedical Engineering, Beihang University, Beijing, PR China

Qingqing Wang,     Key Laboratory of Eco-Textiles, Ministry of Education, Jiangnan University, Wuxi, Jiangsu, China

Xianfeng Wang

Key Laboratory of Textile Science & Technology, Ministry of Education, College of Textiles, Donghua University, Shanghai, China

Innovation Center for Textile Science and Technology, Donghua University, Shanghai, China

Xiao-Xiong Wang,     Collaborative Innovation Center for Nanomaterials & Devices, College of Physics, Qingdao University, Qingdao, China

Xuefen Wang,     State Key Laboratory for Modification of Chemical Fibers and Polymer Materials, Donghua University, Shanghai, People's Republic of China

Qufu Wei,     Key Laboratory of Eco-Textiles, Ministry of Education, Jiangnan University, Wuxi, Jiangsu, China

Dezhi Wu,     Department of Mechanical and Electrical Engineering, Xiamen University, Xiamen, China

Tong Wu,     State Key Lab for Modification of Chemical Fibers & Polymer Materials, College of Chemistry, Chemical Engineering and Biotechnology, Donghua University, Shanghai, China

Meng Xu,     Department of Chemistry and Chemical Biology, Stevens Institute of Technology, Hoboken, NJ, United States

Guilong Yan,     Institute for Frontier Materials, Deakin University, Geelong, Victoria, Australia

Xu Yan,     Industrial Research Institute of Nonwovens & Technical Textiles, Qingdao University, Qingdao, China

Weimin Yang

College of Mechanical and Electrical Engineering, Beijing University of Chemical Technology, Beijing, China

State Key Laboratory of Organic-Inorganic Composites, Beijing, China

Zezhou Yang,     Alan G. MacDiarmid Institute, College of Chemistry, Jilin University, Changchun, PR China

Yang Yi,     Hubei International Scientific and Technological Cooperation Base of Sustainable Resource and Energy, Hubei Key Lab of Biomass Resource Chemistry and Environmental Biotechnology, School of Resource and Environmental Science, Wuhan University, Wuhan, P. R. China

Xia Yin

Key Laboratory of Textile Science & Technology, Ministry of Education, College of Textiles, Donghua University, Shanghai, China

Innovation Center for Textile Science and Technology, Donghua University, Shanghai, China

Jianyong Yu,     Innovation Center for Textile Science and Technology, Donghua University, Shanghai, China

Miao Yu,     Collaborative Innovation Center for Nanomaterials & Devices, College of Physics, Qingdao University, Qingdao, China

Xi Yu,     Key Laboratory of Textile Science & Technology, Ministry of Education, College of Textiles, Donghua University, Shanghai, China

Xufeng Yu,     State Key Laboratory for Modification of Chemical Fibers and Polymer Materials, Donghua University, Shanghai, People's Republic of China

Ghazala Zainab

State Key Laboratory for Modification of Chemical Fibers and Polymer Materials, College of Materials Science and Engineering, Donghua University, Shanghai, China

Innovation Center for Textile Science and Technology, Donghua University, Shanghai, China

Yunyun Zhai,     College of Biological, Chemical Sciences and Engineering, Jiaxing University, Jiaxing, China

Jun Zhang,     Collaborative Innovation Center for Nanomaterials & Devices, College of Physics, Qingdao University, Qingdao, China

Ke-Qin Zhang,     National Engineering Laboratory for Modern Silk, College of Textile and Clothing Engineering, Soochow University, Suzhou, Jiangsu, PR China

Shichao Zhang

State Key Laboratory for Modification of Chemical Fibers and Polymer Materials, College of Materials Science and Engineering, Donghua University, Shanghai, China

Innovation Center for Textile Science and Technology, Donghua University, Shanghai, China

Xiangwu Zhang,     Fiber and Polymer Science Program, Department of Textile Engineering, Chemistry and Science, North Carolina State University, Raleigh, NC, United States

Jing Zhao,     Key Laboratory of Textile Science & Technology, Ministry of Education, College of Textiles, Donghua University, Shanghai, China

Yong Zhao,     Key Laboratory of Bioinspired Smart Interfacial Science and Technology of Ministry of Education, Beijing Key Laboratory of Bioinspired Energy Materials and Devices, School of Chemistry, Beijing Advanced Innovation Center for Biomedical Engineering, Beihang University, Beijing, PR China

Gaofeng Zheng,     Department of Instrumental and Electrical Engineering, Xiamen University, Xiamen, China

Yuman Zhou,     Provincial Key Laboratory of Functional Textile Materials, Zhongyuan University of Technology, Zhengzhou, China

Min Zhu,     Textile Development and Marketing Department, Fashion Institute of Technology, Manhattan, NY, United States

Jin Zou,     Department of Chemistry and Chemical Biology, Stevens Institute of Technology, Hoboken, NJ, United States

Part 1

Fundamentals of Electrospinning

Outline

Chapter 1. Introduction and Historical Overview

Chapter 2. Electrospinning: The Setup and Procedure

Chapter 3. Nanofibrous Materials

Chapter 4. Nanofibrous Structures

Chapter 1

Introduction and Historical Overview

Aijaz Ahmed Babar¹,²,³, Nousheen Iqbal¹,², Xianfeng Wang¹,³, Jianyong Yu³, and Bin Ding³     ¹Key Laboratory of Textile Science & Technology, Ministry of Education, College of Textiles, Donghua University, Shanghai, China     ²State Key Laboratory for Modification of Chemical Fibers and Polymer Materials, College of Materials Science and Engineering, Donghua University, Shanghai, China     ³Innovation Center for Textile Science and Technology, Donghua University, Shanghai, China

Abstract

Nanofabrication is the future of technology and will soon be at the forefront of all manufacturing technologies by providing the design and fabrication of functional nanomaterials, which are potentially capable of responding to all major global challenges of the present and the future. Among all the one-dimensional (1D) nanofabrication techniques reported, electrospinning is the most versatile, is scalable, and is a relatively economical nanofabrication technique that produces long and continuous fibers having diameters in nanoscale. It is capable of tailoring individual fiber structures and can also regulate the morphology of the resultant fibrous mats. The technique is versatile enough to process all kinds of materials, including organic and inorganic polymers, in various forms, such as solutions, emulsions, mixtures, or melts, for generating complex nanofibrous structures, including porous, hollow, core–shell, etc. This chapter provides an overview of various 1D nanomaterial fabrication techniques and discusses in detail the development of the electrospinning technique in historical perspective and finally shares the potential applications of fabricated 1D nanofibrous materials via electrospinning.

Keywords

1D nanomaterials; Electrospinning; Nanofabrication; Nanofiber applications; Nanofibers

1.1. Introduction

1.1.1. Nanofabrication: The Road to Excellence

Nanofabrication, the technology of the future, is the most advanced manufacturing technology in today's world. Because this technology lets scientists reach nearly the theoretical limit of accuracy, i.e., the size of a molecule or atom, it is also believed to be the extreme technology (Mamalis et al., 2004). Indeed, it is basically the manipulation of matter at the nanoscale, which can develop a variety of materials and devices far superior, in terms of performance, efficiency, and durability, to those produced by conventional processes. This manipulation at the nanoscale alters the material characteristics without compromising the fundamental properties of the substrate and makes them intrinsically different and relatively much better compared with their bulk counterparts (Biswas et al., 2012). In addition, it also meets both of the major demands of the manufacturing industry, i.e., ultraprecision and miniaturization; thus this technology is a roadway to excellence in the field of manufacturing.

1.1.2. Potential Applications of One-Dimensional Nanomaterials

Nowadays, nanomaterials are at the center of attention of engineers and scientists because of their ability to alter the performance and capabilities of materials in a number of commercial sectors (Fang et al., 2008, 2011; Zhang and Fang, 2010; Xiao et al., 2011; Wang et al., 2013). Nanomaterials are believed to be at the forefront of the fundamental materials because they provide additional features and aptitudes while maintaining the basic characteristics of the materials. Among all nanomaterials, one-dimensional (1D) nanostructured materials have firmly gained tremendous attraction in recent decades owing to their fundamental features, unique shapes, and potential applications in various fields (Lu et al., 2011; Yuan et al., 2011; Xia et al., 2003). These materials have enough potential to be applied to a very wide range of applications (Fig. 1.1).

Their characteristic features, such as high volume-to-surface area, facilitate the production of lighter weight materials, which is one of the key demands of all manufacturing fields; their ability to be highly hydrophobic and breathable is extremely desired for protective clothing; and their highly porous structure makes them ideal candidates for energy and environmental applications. Hollow fibers with multiple numbers of channels are a value addition in the field of biomedical and tissue engineering. The controlled structures of nanofibers developed from biodegradable and biocompatible sources such as polysaccharides and proteins are very useful in biomedical applications and regulated drug-delivery applications. Moreover, their individual fibers as well as resultant membrane structure can be custom-made to meet the needs of a number of applications. In addition, the growing interest of scientists in using nanofibers in various applications highlights the significance of their potential (Li and Yang, 2016; Kaur et al., 2014), which may also be credited to the easier fabrication with a variety of structural architectures and relatively reasonable production cost.

Figure 1.1  Application potential of 1D nanomaterials. 

© 2006–14 Royal Society of Chemistry. © 2012 Elsevier. © 2017 John Wiley and Sons. Other sources: www.sigmaaldrich.com, www.greenspec.co.uk, www.pacificbluesolar.com, www.penggagas.com, www.nanodic.com.

1.1.3. One-Dimensional Nanofabrication Techniques

The 1D nanoscale materials, such as wires, belts, rods, tubes, spirals, and fibers, owe the most vital importance due to their high length-to-width ratio and huge surface area, and can be produced with various commercial fabrication techniques such as template synthesis, drawing, phase separation, self-assembly, hand-spinning, and electrohydrodynamics (EHD) techniques (Lu et al., 2009; Lauhon et al., 2002; Zach et al., 2000; Hu et al., 1999, 2006; Huang et al., 2001; Barth et al., 2010; Xiao et al., 2010; Shojaee et al., 2010; Jiang et al., 2004; Taylor, 1966; Wang et al., 2006, 2008, 2011; Du and Hsieh, 2008; Dzenis, 2004; Sarkar et al., 2010; Kim et al., 2006).

The drawing technique of nanofabrication is similar in nature to the traditional dry-spinning technique and capable of producing very long single nanofibers. This technique involves three very simple steps, i.e., (1) a drop of polymer solution nearly 1  mL in volume is placed on the substrate, (2) a micropipette is touched to the edge of the drop, and (3) it is pulled back (Fig. 1.2); this backward motion of the micropipette draws the polymer solution enough to turn it into a nanofiber. The standard speed of the up–down moment of the micropipette is about 104  ms−¹, and the diameter of the drawn fiber may range from a few micrometers to several nanometers. Solvent evaporation, polymer nature, and drawing velocity are the parameters that determine the quality of the resultant fibers. The technique is easy to control, is relatively very economical, and also does not require any expert personnel supervision; however, its low production rate and unacceptability for all polymers are major restrictions to its commercial application. A variety of polymeric nanofibers, such as polyvinyl butyl, polymethylmethacrylate, polyvinyl alcohol, polycaprolactone, polyethylene oxide, and hyaluronic acid, have been developed via this technique. In addition, nanofibers from melt have also been reported.

Figure 1.2  Schematic demonstration of 1D nanofiber fabrication via mechanical drawing. (A) A drop of polymer solution is placed on the substrate, (B) a micropipette is touched to the drop, and (C) the micropipette is pulled back.

Figure 1.3  Schematic demonstration of 1D nanofiber production via template synthesis.

The template synthesis technique involves nanosized pores and a variety of materials. The solution is forced through a fibril-shaped solid or hollow tubule and is immediately solidified by a solidification solution (Fig. 1.3). The concept of this technique may be credited to the traditional wet spinning technique in which the polymer solution drawn out through spinnerets is directly passed through a trough containing the fiber solidification solution. A variety of materials, including metal oxides (alumina), metals, semiconductors, or carbons, can be processed via this technique for synthesizing membranes for targeted applications, even without any expert supervision. High production times and inability to develop single nanofibers limit its application at the megascale.

The phase-separation technique of nanofiber fabrication consists of dissolution, gelation, and extraction using a suitable solvent, followed by freezing and drying techniques. A polymer solution in a Teflon trough is converted into a gel with the help of heat treatment and this resultant gel is dried via a freeze-drying process (Fig. 1.4). Polymer concentration and gelation temperature mostly affect the duration of gel. Low and high gelation temperatures lead to the formation of nanoscale fiber networks and platelet-like structures. Fabricated nanofibers are 50–500  nm in diameter and have a porous structure with a network of endless filaments. The type of polymer, type of solvent, gelation temperature, gelation duration, and thermal treatment also affect the nanofibers’ morphology. This technique is simple, inexpensive, and widely used for the fabrication of nanofibers. It makes one by one continuous nanofibers, and mass production is also possible through this technique. However, it suffers some major limitations such as a time-consuming process, laboratory-scale production, lack of structural stability, and difficulty in maintaining porosity and is not applicable for all polymers (He et al., 2014).

Figure 1.4  Schematic demonstration of 1D nanofiber development via the phase-separation technique. 

Reprinted with permission from He, C., Nie, W., Feng, W., 2014. Engineering of biomimetic nanofibrous matrices for drug delivery and tissue engineering. Journal of Materials Chemistry B 2, 7828–7848. © 2014 Royal Society of Chemistry.

1.2. Electrospinning

1.2.1. Overview

Electrospinning is simple, and is potentially the most effective and advanced EHD technique being used for the production of continuous fibers with diameters down to a few nanometers. It shares the characteristic features of two conventional processes, i.e., electrospraying and conventional dry or melt spinning. The process involves the use of high voltage for inducing the formation of a liquid jet, which is soon solidified either by evaporating the solvent or by freezing the melt to ensure nanofiber fabrication (Fig. 1.5). This versatile process can be applied to natural as well as synthetic polymers, polymer alloys, metals, and ceramics (Greiner and Wendorff, 2007). A variety of fibrous architectures, such as porous fibers, core–shell fibers, hollow fibers, and helical fibers, etc. can be produced by the electrospinning technique using certain special tools. Moreover, the process is capable of producing a diverse range of single-fiber structures as ordered arrangements of fibers. Depending on the physical, biological, or chemical attributes, fibers produced using electrospinning are of great interest for a range of applications, including filtration, biomedicine, sensors, protective clothing, and so on. Since the late 1990s, the electrospinning process has not only been intensively reexamined by laboratories to ensure its acceptability at the megascale, but has also been extensively applied in industry (Thavasi et al., 2008; Dong et al., 2011; Bhardwaj and Kundu, 2010).

Figure 1.5  (A) Schematic illustration of the basic electrospinning setup. (B) Schematic drawing of the looping part of the jet showing a sequence of bending instabilities. PPENK , poly(phthalazinone ether nitrile ketone). 

(A) Reprinted with permission from Wang, G., Zhang, H., Qian, B., Wang, J., Jian, X., Qiu, J., 2015. Preparation and characterization of electrospun poly(phthalazinone ether nitrile ketone) membrane with novel thermally stable properties. Applied Surface Science 351, 169–174. © 2015 Elsevier. (B) Reprinted with permission from Reneker, D.H., Yarin, A.L., 2008. Electrospinning jets and polymer nanofibers. Polymer, 49, 2387–2425. © 2008 Elsevier.

1.2.2. History of Electrospinning

Electrospinning, also known as electrostatic spinning, is not a very new but yet is a very powerful nanofiber fabrication technique. It is versatile enough to produce fibers on micro- and nanoscales and is believed to be a variant of the electrospray process. The first record claiming the electrostatic attraction of liquids is traced back to the 16th century, reported by Gilbert, the president of the Royal College of Physicians (Wendorff et al., 2012; Tucker et al., 2012). He claimed that if a properly charged piece of amber and a water droplet are brought close enough to each other, the latter would form a cone shape, and small droplets would be ejected from the tip of the cone. About 270  years later, Bose synthesized aerosols using high electric potentials in 1745 (Lin et al., 2012; Greiner and Wendorff, 2007). Later on, in 1882, Rayleigh calculated the maximum amount of charge that causes a liquid drop of definite size to burst by overcoming the surface tension of the droplet. He also explained that the stability of an ascending liquid jet would first increase with increasing electric charge; however, when the electric charge exceeds a certain limit, then it will destabilize the liquid jet (Wang, 2008; De Vrieze and De Clerck, 2009).

In the early 20th century, Morton and Cooley demonstrated the phenomenon of the electrospinning process and discovered the possibility of fabricating tiny fibers via electrospinning, and in addition, they first patented the devices using electric charge to spray liquids: four types of indirectly charged spinning heads, a conventional head, a coaxial head, an air-assisted model, and a spinneret featuring a rotating distributor, were proposed (Ding and Yu, 2014; Morton, 1902; Cooley, 1902, 1903). W.B. Wiegand and E.F. Burton further described the relationship between charge and surface tension to examine electrical effects on water streams (Burton and Wiegand, 1912; Wang et al., 2006). John Zeleny, a physicist working at the University of Minnesota, published a series of papers between 1907 and 1920 describing electrical discharge from liquid as well as solid surfaces. He determined that the diameter of the electrodes was the primary factor, rather than the shape of the electrodes, that influenced the discharge current. He also analyzed the effect of humidity and concluded that an increase in humidity required more potential to maintain the predefined current flow. Later on, he examined fluid droplet behavior at the end of metal capillaries and determined the distortion tendency of a hemispherical liquid droplet under high voltage, which helped in developing the mathematical model for determining fluid behavior under electrostatic forces. This is also believed to be the initiation of modern needle electrospinning (Lin et al., 2012; Zeleny, 1914, 1917).

K. Hagiwara, Professor at Imperial University Kyoto, reported on the use of electricity for regulating the molecular structure of a colloidal liquid viscose precursor that could align colloidal components leading to highly lustrous fibers, i.e., free of irregular aggregation of the particles. In addition to viscose, other substrates, such cellulose acetate and nitrocellulose, gelatin, albumen, and natural silk solutions, were also run through Professor Hagiwara’s equipment (Kiyohiko, 1929). W. A. Macky from New Zealand explained that it is the ionized gas or vapor particles that make a flow of current that breaks the liquid drop during flight, rather than the flight of the charged liquid drop (Macky, 1931, 1937).

Further progress toward commercialization was made by A. Formhals (United States), who published a series of 22 patents from 1931 to 1944, which are believed to be a key contribution to the development of electrospinning (Anton, 1934). Anton explained the physical setup for producing polymer filaments using electrostatic force. He intended to develop yarns by gathering up the fibers for further processing, which was a very critical job. Initially, Anton designed a machine having a sawtoothed rotating fiber emitter dipped in a polymer solution trough (Formhals, 1934). Fibers were emitted from the wetted tips with the help of an electric charge toward the rotating collector. Later on, Anton planned tapered nozzle–shaped fiber emitters and aimed to collect short staple fibers; staple fibers with controlled length were produced by disrupting the current flow to the spinning heads of the machine (Formhals, 1937; Anton, 1938). In addition, Anton also proposed cospinning of fibers with opposite charge to produce a product with no net charge, and made serious efforts to devise winding devices to gather up the fiber in a usable form (Anton, 1939, 1940, 1943).

Charles Ladd Norton, an American physicist, who had experience of powering Crookes tubes with high voltage, was the first to introduce melt spinning using a combined electrostatic and air-jet assist method, and also made efforts to prepare lofted fibers for insulation or packaging applications (Williams, 1940). Following this, Games Slayter produced glass wool fiber using melt spinning, which was later commercialized by the Owens Corning fiberglass company and was used by naval ships for fire protection (Slayter, 1938).

In the 1930s, N.A. Fuchs (USSR) and his coworkers introduced the theory of ultrafine fibrous materials and developed electrospun fibers for filter materials. For this contribution they were awarded the Stalin Prize. Based on their work, a factory was installed to fabricate electrospun fibers for gas masks using cellulose acetate and a solvent mixture of ethanol and dichloromethane. In the 1950s, using the Petryanov filter, a particulate filter mask, the Lepestok, was developed for the nuclear industry. B. Vonnegut (Vonnegut and Neubauer, 1952) and V. Drozin (Drozin, 1955; Vonnegut and Neubauer, 1952) investigated liquid jet production under electrostatic force and observed that uniform-sized droplets of about 1  μm were formed during the process, which repelled one another in the case of having like charges. The generation of these droplets was attributed to the dielectric constant of fluid droplets; moreover, dipole moment, conductivity, and refractive index were observed as process-limiting factors.

The output of spun filtration materials had reached as much as 20  million  m² per annum by the 1960s. Polymer substrate was pushed through spinnerets under the exceptionally high voltage of 100  kV, and the resulting liquid stream was bifurcated, leading to high volume throughput. It was then Sir Geoffrey Ingram Taylor who made a significant advancement in the theoretical underpinning of the electrospinning process during 1964–65. Taylor designed a mathematical model of the conical shape of the fluid droplet in an electric field. This characteristic droplet shape is now known as the Taylor cone. In 1971 Baumgarten found that fiber diameter depends on process and substrate parameters such as solution viscosity, jet radius and length, and applied voltage. Taylor also reported, with the help of his devised method for photographing electrospun fibers during flight, that only a single fiber is spun at a time and that the filament forms many loops, which fall to the electrical ground. In addition, he described the electrospinning of acrylic, whereas Larrondo and S.J. Manley published a series of articles on the subject of electrospinning of polymer melts. They also launched a melt electrospinner, in which a dead weight was used to push the polymer through a barrel to the spinning tip, which was then drawn rapidly using electrostatic force. In the meantime, certain efforts in the commercialization of the electrospinning process were also undertaken in the 1970s. A series of patents was submitted by Simm, from the Bayer Company, on the electrospinning of plastics, and the first practical application advised for electrospinning was for the nonwoven industry.

The electrospinning process became popular only after the 1990s, when numerous research groups, especially those of Reneker (University of Akron) and Wendorff, picked up the process. It was then established that several organic polymers could be electrospun into nanofibers. Since then, a number of researchers have entered this field and the quantity as well as quality of research papers has exponentially increased, from just a few papers per annum to over 4000 in 2017 (Fig. 1.6). Increasing numbers of patents, books, and review papers about electrospinning applications have been reported in recent years, and over 500 research institutes and universities around the globe working in the field of electrospinning signify its popularity and provide insight into the most prominent aspects of the process. Increasing interest and active involvement of certain commercial companies, such as Nano Technics, eSpin Technologies, Elmarco Ltd., and Kato Tech, witness the huge impact and significance of electrospinning in the field of materials science. Some companies such as Freudenberg and Donaldson Company have been earning significant capital by reaping the benefits of electrospun nanofibers since the late 1990s or even earlier.

In short, this rapid and intensive research carried out since the beginning of the 21st century in the field of electrospinning can be summarized as follows: (1) an extensively enhanced number of polymers and composites are being electrospun; (2) the comprehensive in-depth comprehension of nanofiber fabrication has increased; (3) a very broad range of fiber and membrane structures, including those inspired from nature, have been made possible; (4) it is possible to develop multicomponent, composite, and inorganic fibers; and (5) the focus of research has been transformed from fabrication to application, and now it is being centered on the industrialization of this process.

Figure 1.6  Number of publications from 2001 to January 24, 2018, with the keyword electrospinning. 

From ISI Web of Science.

1.2.3. Modern Electrospinning Technology

The versatile maneuverability of electrospinning to produce nanofibers with regulated individual fibers as well as resultant membrane structures, the controlled inter- and intrafiber porosity, and the ability to produce meticulous fiber orientations and dimensions make it a simple but powerful fiber manufacturing technique. In addition, easier process control and lower production costs are potential reasons for its global attention. Randomly oriented structures of fibers obtained from electrospinning are being utilized in numerous fields. However, this random orientation of electrospun nanofibers limits their broader acceptability in the fields of biomedical and electronic devices (Supaphol et al., 2011). Therefore, it is extremely necessary to fabricate nanofibers with controlled fiber structure and ordered fiber orientation via electrospinning to make full use of their potential and enhance their acceptability in electronic devices and biomedical applications, which require well-arranged fiber alignment and special fiber structures (Greiner and Wendorff, 2007).

Many groups are engaged in developing aligned fiber arrays produced via electrospinning with the help of custom-made collectors. As a result, various patterned fiber architectures (Fig. 1.7) have been successfully synthesized by various groups with certain process modifications, such as insulation gaps introduced between conducting collectors demonstrated in uniaxially aligned fiber mats (Rasel, 2015). It is also reported that high-speed rotating rollers can also produce aligned fibers; however, the collector rotation speed and fiber orientation strongly influence the resultant nanofiber properties. In addition, this approach facilitates the direct integration of tailorable configured nanofibers, which may be a key support for manufacturing nanofiber-based devices (Wang et al., 2013; Woodruff and Hutmacher, 2010; Pan et al., 2008).

Figure 1.7  Schematic demonstration of some electrospun nanofiber architectures and their corresponding applications. 

Reprinted with permission from Wu, J., Wang, N., Zhao, Y., Jiang, L., 2013. Electrospinning of multilevel structured functional micro-/nanofibers and their applications. Journal of Materials Chemistry 1, 7290–7305. © 2013 Royal Society of Chemistry.

In addition to aligned or patterned nanofibers, the process is also capable of producing a very wide range of fibrous structures, including core–shell (Sun et al., 2003; Zhang et al., 2009), tube-in-tube (Mou et al., 2010), multicore cablelike (Hiroshi et al., 2007), rice grain shape (Shengyuan et al., 2011), helical (Kessick and Tepper, 2004; Shin et al., 2006), ribbon-like (Koombhongse et al., 2001), necklace-like (Jin et al., 2010; Lu et al., 2006), multichannel tubular (Zhao et al., 2007), nanowire-in-microtube (Chen et al., 2010), firecracker shape (Chang, 2011), and hollow (Li and Xia, 2004) fiber structures (Wu et al., 2013). Moreover, the provision of high specific surface area and feasibility to control pore size along with certain chemical, physical, thermal, and mechanical characteristics of fabricated nanofibers indicate the significance of the process (Huang et al., 2003; Zhu et al., 2008).

The versatile nature of the electrospinning process and its ability to synthesize numerous fiber structures from all kinds of materials (i.e., organic as well as inorganic polymers or the combination both) and various input forms, including melts, solutions, emulsions, and mixtures, have recommended it for use in different fields ranging from the hottest fields of energy generation, defense, and security to complicated fields like health care, biomedicine, biotechnology, and environmental engineering (Tran et al., 2011). Several modifications in the basic electrospinning process have been made to meet the desired needs of these applications (Fig. 1.8). These modified electrospinning techniques include tipless electrospinning, edge electrospinning, multijet electrospinning, and electroblowing to enhance the throughput rate of the process to render the electrospun nanofibers acceptable on a larger scale. In addition, the enormous amount of research since 2008 has concluded that nanofibers offer huge potential for various fields; however, fiber diameters yet need to be reduced to tens of nanometers (<50  nm), which is very critical and challenging task, to achieve ultrasensitive sensors, ultrafiltration, catalysis, etc. Therefore, as of this writing, researchers are focused on developing such a process that offers not only high throughput, but also fibers with extremely small diameter along with controlled fiber morphology.

1.3. Nanofibers: Solving Global Issues

As discussed earlier, intensive research is being carried out on electrospun nanofibers to comprehend the theoretical and practical aspects of their fabrication process and the characteristics of the resultant nanofibers. Thus, after long and untiring efforts, scientists are successfully able to tailor the fiber morphology and aggregate structures, which has resulted in numerous applications for electrospun nanofibers reported by various research institutes via scientific publications. Still, intensive research is being carried out to learn more and more about nanofibers and their corresponding possible applications for solving various issues around the globe (Mongwaketsi, 2014).

Electrospun nanofibers, when applied in the fields of energy and environmental engineering, play a vital role in solving the current energy and environmental issues that are alarming threats to the world today. Owing to their delicate fabrication, specially designed functional electrospun nanofibers have been employed in the energy sector, including in fuel cells (Chevalier et al., 2017), organic and hybrid solar cells (Mohamed et al., 2017), lithium ion batteries (Aravindan et al., 2015), dye-sensitized solar cells (Singh et al., 2017), hydrogen storage (Kharel et al., 2017), carbon dioxide capture (Iqbal et al., 2017), and supercapacitors (Iqbal et al., 2016, 2017a,b). In addition to these energy-related applications, nanofibers have been widely utilized in the field of environmental engineering to fulfill the need for clean water and air, the biggest threat to human health around the globe (Vaseashta et al., 2008). Thus, functional nanofiber use has been reported for air filtration, liquid filtration, sensors, oil spill cleanup, photocatalysis, electromagnetic shielding, adsorbents, self-cleaning products, etc.

Figure 1.8  Various needle-based spinneret designs and collector shapes for synthesizing typical fiber structures. 

Reprinted with permission from Aravindan, V., Sundaramurthy, J., Suresh Kumar, P., Lee, Y.-S., Ramakrishna, S., Madhavi, S., 2015. Electrospun nanofibers: a prospective electro-active material for constructing high performance Li-ion batteries. Chemical Communications 51, 2225–2234. © 2015 Royal Society of Chemistry.

Moreover, the application range of nanofibers is not limited to the energy and environmental engineering fields; they also provide value additions in the most critical fields of defense, security, and health care. Since security, firefighter, and medical personnel, among others, are always exposed to known and unknown hazardous attacks, they require an extreme level of protection from both hazardous chemicals and microorganisms (Ratner and Ratner, 2004). Nanostructures have enabled the design of lighter and more effective protective suits by virtue of their light weight, high surface area, and breathable porous nature (Sheng et al., 2016, 2017; Li et al., 2015, 2016; Yang et al., 2016). Nanofiber-enabled protective structures have taken personnel protection to the next level because of their ability to filter and destructively decompose harmful toxins without compromising the comfort of the protective garment (Turaga et al., 2012; Babar et al., 2017, 2018). Similarly, nanofiber employment has been reported to be very efficient and economical in a very wide range of applications in field of health care, which include medical implants, controlled drug delivery, tissue engineering, wound dressings, and medical textiles (Song et al., 2017; Ceylan et al., 2017; Irani et al., 2017; Laha et al., 2017; Zilberman and Elsner, 2008; Dash et al., 2011; Tansaz et al., 2017; Grande et al., 2017; Aragon et al., 2017; Zhou et al., 2017; Perumal et al., 2017).

1.4. Outlook

This chapter summarized the electrospinning process and the history of its development, with a brief discussion about the potential applications of electrospun nanofibers. Recent progress in electrospinning technology provides significant evidence for the potential role of electrospun nanofibers in defense and security, biomedicine, environmental protection, energy conversion, and storage applications (Fig. 1.9). Electrospun fibrous mats used as protective clothing would not only provide excellent protection from both chemical and biological attacks but also maintain the comfort of the garment, which plays a very critical role in the performance of the wearer. The use of functional nanofibers in electronic devices would enhance the performance, efficiency and cycle life of the fabricated devices. Moreover, nanofiber based filters for fluid filtration have given excellent protection to the environment and public health, which was never possible with conventional filtration materials.

Furthermore, the large-scale production of nanofibers has become possible to some extent; however, it is yet a very challenging job to fabricate bead-free fibers with diameters less than 50  nm. Therefore, extensive research is being carried out on developing nanofibers with <50-nm diameters. Their successful fabrication on a large scale would open new doors to achieving extraordinary performance in numerous applications such as ultrasensitive sensors, ultrafiltration, catalysis, etc.

Figure 1.9  Some of the major potential application categories of nanofibers.

Acknowledgments

This work is supported by the National Natural Science Foundation of China (Nos. 51473030, 51503028, and 51673037), the Shanghai Committee of Science and Technology (No. 15JC1400500), the Shanghai Rising-Star Program (No. 16QA1400200), and the Fundamental Research Funds for the Central Universities (No. 2232016A3-03).

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Chapter 2

Electrospinning

The Setup and Procedure

Yun-Ze Long¹,², Xu Yan², Xiao-Xiong Wang¹, Jun Zhang¹, and Miao Yu¹     ¹Collaborative Innovation Center for Nanomaterials & Devices, College of Physics, Qingdao University, Qingdao, China     ²Industrial Research Institute of Nonwovens & Technical Textiles, Qingdao University, Qingdao, China

Abstract

Electrospinning is a beneficial and effective technology to produce continuous nanofibers by electric force. According to the mechanism of the electrospinning process, the basic electrospinning setup contains a high-voltage system, spinneret, and collector. To control the electrospun fiber’s structure and for practical applications, great efforts have been made to modify the electrospinning setup and procedure. In this chapter, the designs of electrospinning setups are discussed. In Section 2.1, the basic electrospinning setup and parameters of the electrospinning process are discussed. The modification of collectors and spinnerets is discussed in Sections 2.2 and 2.3. Moreover, for a whole setup, portable and industrial electrospinning devices are discussed in Sections 2.4 and 2.5.

Keywords

Collector; Electrospinning mechanism; Electrospinning setup; High-voltage system; Industrial electrospinning device; Portable electrospinning device; Spinneret

2.1. Basic Electrospinning Setup and Procedure

It is known that the formation of nanofibers through electrospinning is based on the uniaxial stretching or elongation of a viscoelastic jet derived from a polymer solution or melt (Chronakis, 2005; Huang et al., 2003; Teo and Ramakrishna, 2006; Park et al., 2007; Greiner and Wendorff, 2007; Bhardwaj and Kundu, 2010). Here, we focus on the solution electrospinning process only; melt electrospinning will be discussed in Chapter 11. A typical electrospinning setup is mainly composed of a high-voltage power supply, a needle spinneret, and a grounded conductive collector (Chronakis, 2005; Huang et al., 2003; Teo and Ramakrishna, 2006; Park et al., 2007; Greiner and Wendorff, 2007; Bhardwaj and Kundu, 2010), as shown in Fig. 2.1. During the electrospinning process, when high voltage is supplied, the polymer solution droplet at the needle tip deforms into a cone shape (generally called a Taylor cone) under the electrostatic forces. The strong electrostatic force has been regarded as the driving force for initiating the electrospinning process. Under the force of a strong electrostatic field, the charged solution jet at the spinneret tip changes its size to maintain the force balance. With increasing electrostatic-field intensity, the induction charges on the surface repel each other and produce shear stresses. These repulsive forces act in the direction opposite to the surface tension, which leads to the extension of the solution drop into a Taylor cone and plays a role in initiating the surface. When the electrostatic field achieves the critical voltage Vc, the balance of repulsive forces is broken and thus a charged jet ejects from the tip of the conical drop. The critical voltage Vc for electrospinning is given by the following expression based on Taylor's calculation (Taylor, 1969):

(2.1)

where H is the distance from the spinneret tip to the collector, h is the length of the liquid column, R is the inner radius of the spinneret, and γ is the surface tension of the spinning solution (units: H, h, and R in cm, γ in dyn/cm). The factor 0.09 is inserted to predict the voltage. After the elongation of fibers and evaporation of solvent or melt cooling, solid ultrathin fibers are eventually deposited onto the collector. Finally, a thin nonwoven film with fibrous architecture is formed with the fiber depositing continuously onto the collector.

Figure 2.1  Schematic diagram of a conventional electrospinning setup, as well as environment, solution, and electrospinning variables.

Despite electrospinning's easy use and low cost, there are a great quantity of processing parameters, which could highly influence fiber generation and nanostructure. Fig. 2.1 illustrates the operating parameters and processing conditions in an electrospinning procedure. The optimized process parameters are necessary to help the stabilization of electrospun ultrathin fibers. Here, some important electrospinning process parameters are discussed in the following sections.

2.1.1. Applied Voltage

As shown in Fig. 2.2, the applied voltage has several influences on the electrospinning process, since it affects the amount of charges applied to the solution. Increasing voltage will accelerate the electrospinning jet and this may result in greater volume of solution drawn from the tip of the needle. If the feed rate of the solution is fixed, this will result in a smaller and less stable Taylor cone (Zhong et al., 2002) and may eventually cause the Taylor cone to recede into the needle (Deitzel et al., 2001). There are several contradicting reports on the effect of higher applied voltage on fiber morphology. It is expected that a higher applied voltage will lead to greater