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About this book

This Handbook covers all aspects related to Nanofibers, from the experimental set-up for their fabrication to their potential industrial applications. It describes several kinds of nanostructured fibers such as metal oxides, natural polymers, synthetic polymers and hybrid inorganic-polymers or carbon-based materials.
The first part of the Handbook covers the fundamental aspects, experimental setup, synthesis, properties and physico-chemical characterization of nanofibers. Specifically, this part details the history of nanofibers, different techniques to design nanofibers, self-assembly in nanofibers, critical parameters of synthesis, fiber alignment, modeling and simulation, types and classifications of nanofibers, and signature physical and chemical properties (i.e. mechanical, electrical, optical and magnetic), toxicity and regulations, bulk and surface functionalization and other treatments to allow them to a practical use. Characterization methods are also deeply discussed here. The second part of the Handbook deals with global markets and technologies and emerging applications of nanofibers, such as in energy production and storage, aerospace, automotive, sensors, smart textile design, energy conversion, tissue engineering, medical implants, pharmacy and cosmetics. Attention is given to the future of research in these areas in order to improve and spread the applications of nanofibers and their commercialization.

Table of Contents


Fundamental Aspects, Experimental Setup, Synthesis, Properties, and Characterization


1. Nanofiber Technologies: History and Development

Nanofibers are defined as fibers with diameters on the order of 100 nm. Nanofibers have been considered one of the top interesting studied materials for academicians and one of the greatest intriguing materials for modern industry. Nanofibers provide great opportunities for creating products with new properties via various physical and chemical modifications during or following the production process. Nanofibers bring promising solutions for fundamental problems in our life in various fields such as energy, environmental, and medical treatments. Researchers have turned to the development of a number of nanofiber fabrication techniques such as electrospinning, template-assisted synthesis, melt-blowing, bicomponent spinning, force-spinning and flash-spinning, chemical vapor deposition, and physical vapor deposition. However, the electrospinning is the widely used technique to produce continuous nonwoven nanofiber mats. In this chapter, a brief introduction to nanoscience and nanotechnology was discussed, and then the history and development of nanofiber technologies and production techniques are presented. In the following, types and classifications of nanofibers based on their origin and morphologies and their unique properties are explained, and finally, some current applications and their future perspectives are discussed.

Ahmed Barhoum, Rahimeh Rasouli, Maryam Yousefzadeh, Hubert Rahier, Mikhael Bechelany

2. Fabrication of Nanofibers: Electrospinning and Non-electrospinning Techniques

Fabrication of nanofibers has received increasing attention due to their unique properties and wide range of applications in energy production, energy storage, environmental protection and improvement, healthcare, and many more. Nanofibers provide a good material system that can improve the electrical, optical, thermal, and mechanical properties of many types of bulk materials. To date, various materials (metal, metal oxides, ceramics, polymers, and carbon) have been fabricated into nanofibers by electrospinning and non-electrospinning. Hence, several non-electrospinning techniques were developed to improve the production yield of nanofibers. Some of these techniques include solution blowing (or air-jet spinning), drawing techniques, template synthesis, centrifugal spinning, phase inversion/separation, and freeze/drying synthesis. This chapter discusses the designing, fabrication, and properties of nanofibers for various morphologies and compositions. A comprehensive review is presented on electrospinning and non-electrospinning techniques, along with their synthesis mechanisms. The chapter splits the nanofiber fiber fabrication techniques into: physical synthetic routes (e.g., mechanical milling, physical vapor deposition, laser ablation, and electrospinning) and chemical synthetic methods (e.g., Chemical vapor deposition, hydrothermal, sol-gel, template assisted synthesis, sonochemical and microwave synthesis, and electrochemical deposition).

Dalapathi Gugulothu, Ahmed Barhoum, Raghunandan Nerella, Ramkishan Ajmer, Mikhael Bechelany

3. Different Methods for Nanofiber Design and Fabrication

Over the past few years, there has been a tremendous increase in the demand for polymeric nanofibers which are promising candidates for various applications including tissue engineering, blood vessels, nervous system, drug delivery, protective clothing, filtration, and sensors. To address this demand, researchers have turned to the development of various techniques such as several non-electrospinning and several electrospinning techniques for the fabrication of nanofibers. In this chapter, a comprehensive and systematic review covering all the techniques used to produce nanofibers have been discussed. Some of the techniques include drawing techniques, spinneret-based tunable engineered parameter (STEP) method Spinneret-based tunable engineered parameters (STEP) method , phase separationPhase separation, self-assemblySelf-assembly, template synthesisTemplate synthesis, freezeFreeze-drying synthesis, and interfacial polymerization of nanofibers. The electrospinning technique is well referenced for its effectiveness in the production of nanofibers. The past two decades have witnessed the development of the traditional electrospinning technique, and many derivative methods have been emerged such as multi-jet electrospinning, needleless electrospinning, bubble electrospinning, electro-blowing, cylindrical porous hollow tube electrospinning, melt electrospinning, coaxial electrospinning, forcespinning, flash-spinning, self-bundling electrospinning, nanospider electrospinning, charge injection electrospinning, etc.This chapter also highlights some of the advantages and disadvantages of each production process. In addition, schematic diagrams of various methods for nanofiber production and the features of nanofibers that can be produced using each technique are illustrated.

Ibrahim Alghoraibi, Sandy Alomari

4. Advances in Melt Electrospinning Technique

Melt electrospinning is a technique capable of producing micro- and nanofibers with the advantages of being eco-friendly, cost-effective, and applied in many areas such as nonwovens with high performance, biomedicine, high-efficiency filtration, oil sorption, and many others. This chapter describes the current trends on melt electrospinning including advancements in the technique, processing parameters, materials, apparatus, and areas of applications. Melt differential electrospinning which is a new technique for nanofiber production invented by our innovation team of advanced polymer processing has been introduced. Future perspectives on melt electrospinning are also proposed.

Mahmoud Mohammed Bubakir, Haoyi Li, Ahmed Barhoum, Weimin Yang

5. Design of Porous, Core-Shell, and Hollow Nanofibers

Electrospinning can be used to prepare various organic or inorganic nanofibrous structures. These structures could be related to the nanofibers arrangement relative to each other, as random, aligned, 3D, and yarn, or they could be related to the single nanofiber structure and morphology, or both. In the electrospinning process, nanofibers could be produced to have surface or internal porous structure. Considering the type of material which is used, different methods are introduced to get the desired porosity in nanofibers such as chemical etching, blend solution, effect of humidity, and different post-treatment methods. Also, by using different methods, it is possible to produce core-shell nanofibers or hollow ones. For fabrication of the core-shell nanofibers, one method is to use the special coaxial nozzle. However, there are other techniques to get core-shell nanofibers like emulsion precursor solution, different methods of surface coating, and so on. Based on the diversity of techniques, in this chapter an attempt is made to cover the most usable methods to get the porous, core-shell, and hollow nanofibers and present some applications for each.

Maryam Yousefzadeh, Farzaneh Ghasemkhah

6. Polymer-Based Nanofibers: Preparation, Fabrication, and Applications

Polymer-based nanofibers as an important group of materials have attracted considerable attention of research and industrial areas. Polymer nanofibers with diameters in submicrometer (<1 μm) possess unique properties including large specific surface area per unit mass, which facilitated adding functionalities to surface for specific applications.Typically, polymer nanofibers have been synthesized by electrospinning, spinneret-based tunable engineered parameters (STEP) or drawing techniques, template synthesis, phase separation/inversion, self-assembly, solution blowing (air jet spinning), forcespinning (centrifugal spinning), and interfacial polymerization of nanofibers. The most common method is electrospinning due to its feasibility, cost-effectiveness, ability to fabricate continuous fibers from various polymers, and mass production. However, pros and cons of synthesis methods will also be presented. Furthermore, characterization methods of polymer nanofibers and effective factors on nanofibers will be provided.Polymer nanofibers are fabricated from both natural and synthetic polymers. Polymer blends are also used to improve biodegradability in medical applications and conductivity in sensors and neural tissue engineering.This chapter will also present recent developments of polymer nanofiber applications as scaffolds for tissue engineering, wound dressing, drug delivery, filters, protective clothing, sensors, and reinforcement in composite materials.

Masoumeh Zahmatkeshan, Moein Adel, Sajad Bahrami, Fariba Esmaeili, Seyed Mahdi Rezayat, Yousef Saeedi, Bita Mehravi, Seyed Behnamedin Jameie, Khadijeh Ashtari

7. Carbohydrate-Based Nanofibers: Applications and Potentials

Carbohydrate polymers have recently attracted great interest from academia and industry as one of the most abundant polymers in the world. Homopolymers or copolymers of monosaccharides, known as polysaccharides, are important part of carbohydrates and polymer materials with different sources from plants, microbes, and animals. Various structures and sources provide different chemical and mechanical properties and in result different applications. Carbohydrates are inexpensive materials, easily available, and renewable resources which present important characteristics including hydrophilicity and biocompatibility into polymeric systems. In this chapter potentials and applications of carbohydrate materials such as chitosan, chitin, cellulose, and alginate or their combinations in nanofiber form will be reviewed.

Sajad Bahrami, Moein Adel, Fariba Esmaeili, Seyed Mahdi Rezayat, Bita Mehravi, Masoumeh Zahmatkeshan

8. Native Crystalline Polysaccharide Nanofibers: Processing and Properties

Native polysaccharide nanocrystals have gained increasing interest as fibrous reinforcement in nanocomposites. Unique mechanical properties combined with biodegradability and renewability have placed them as alternative for designing environmentally friendly materials. The source origin and processing have a large impact on the nanofiber dimensions and properties. Most of the studies have been devoted to cellulose and chitin nanocrystals which are organized into fiber bundles in nature. Cellulose nanofibers can be obtained from animal, bacterial, algal, and plant sources. Chitin fibrils constitute, for example, fungal cell walls and arthropod exoskeletons. Based on processing, one defines two major families of polysaccharide nanofibers (whiskers and nanofibrils of polysaccharide). The preparation of the elementary whisker monocrystals has been achieved by acid hydrolysis, which allows collecting them after cleavage of the amorphous domains of the original substrates. Alternatively, the nanofibrillated material constitutes the other family, which results from the peeling of native microfibrils into a network of nanofibrils. The microfibril delamination is often performed with mechanical devices. Chitosan is the deacetylated derivative of chitin. Nevertheless, the preparation of chitosan crystalline nanofibrils that preserve the native directional packing is challenging. The preparation of chitosan nanofibril networks was recently reported by means of a chitosan mild hydrolysis at the solid state. This chapter reviews the methodologies used to produce crystalline nanofibers of polysaccharide with preserved native structural packing. Nanofibers of polysaccharides cellulose, chitin, and chitosan will be the focus of this review. The methods used to characterize these nanofibers will be revised, and the nanofiber properties will be discussed.

Pieter Samyn, Anayancy Osorio-Madrazo

9. Mixed Metal and Metal Oxide Nanofibers: Preparation, Fabrication, and Applications

The review presents the overview of the design, synthesis, fabrication, and applications of metal and metal oxide-based nanofibers. Furthermore, it also describe the recent trends in methodologies used and types of nanofibers produced; including polymers, nanoparticles and ionic liquid based nanofibers. The great deal of interest and attention is currently being focused by the scientific community on nano- and mesostructured materials. The quest for the establishment of these classes of nanosystems has created new challenges in their research development processes. Nanofibers are fibers with the size of around 100 nm, which are made from various inorganic materials such as ceramics, metal, and metal oxides. This review describes the synthesis, fabrication, and some of the selected applications of nanofibers in recent years. Mixed metals and their oxides give rise to a significant class of nanofibers with fascinating properties. The metals and metal oxides which are used for the synthesis of nanofibers are, inter alia, Si, Ba, Ti, Mn, Cu, Fe, Sn, Sb, Ni, Mo, CeO2, TiO2, CuO, Fe2O3, MnO2, SnO2, and NiCo2O4. Generally, the important parameters such as morphology, size distribution, and composition in homogeneous systems are difficult to control, and, in the fabrication of new materials, the nanometer size of the dimensions should be maintained within the accepted ranges. Presently, microscale hierarchically structured nanomaterial-based nanofibers are focused and developed toward future technology. Moreover, the increasing prominence and significance of the nanofiber industry are, in recent years, due to the heightened awareness of their capability to improve the performance of different forms of filter media. In addition, nanofibers have fascinating properties and advantages such as high surface area, small pore size, and high pore volume, over conventional fibers. Generally, nanofibers are applied in various fields such as wound dressings, filtration and cleaning processes, tissue engineering scaffolds, drug release materials, energy storage, environmental engineering, defense, and security systems.

Vasanthakumar Arumugam, Kandasamy G. Moodley

10. Various Techniques to Functionalize Nanofibers

Surface properties of a material control cell adhesion, adsorption, wettability, and colloidal stabilization. The surface functionalization of biomaterials or metals improves the biocompatibility and facilitates the cell attachment. It is established that the fabrication of superhydrophilic and superhydrophobic surface is feasible by surface functionalization. Surface-functionalized materials are found to be suitable to enhance cell material interaction. Hence, various surface functionalization methods carried out using procedures which involved covalent and noncovalent bonds are discussed. However, selection of a suitable functionalization and a reagent based upon the surface chemistry of the material is indispensable. This chapter mainly deals with the various surface functionalization techniques and describes the relevant approaches for activating the surface of the fibers. It provides the basic understanding about the selection of suitable reagent based on the available functional groups.

Sakthivel Nagarajan, Sebastien Balme, S. Narayana Kalkura, Philippe Miele, Celine Pochat Bohatier, Mikhael Bechelany

11. Dyeing of Electrospun Nanofibers

Dyeing and colorimetric properties on different types of nanofibers is promising for potential apparel applications. Apart from the functional properties electrospun cellulose acetate nanofibers, cellulose nanofibers, Nylon 6 and Nylon 6,6 nanofibers, Polyester nanofibers, and polyurethane nanofibers are being widely studied recently for dyeing with different dyes and techniques. In general, the polymers solution prepared and converted into nanofibers using electrospinning. The prepared nanofibers are continued to obtain a web thickness varied between 10 um and 100 um, depending on the type of polymer being electrospun. The nanofiber web is then dyed with specific dyes by either batch wise or padding method. We also report using ultrasonic energy in dyeing process to enhance color strength (K/S) values and efficiency of process. This chapter covers range of nanofibers that can be dyed with different dyes and techniques with achieving enough color strength, color fastness values with unaltered morphology, and chemistry of nanofibers. The dyed electrospun nanofibers can potentially be considered for advanced apparel applications.

Muzamil Khatri, Umair Ahmed Qureshi, Farooq Ahmed, Zeeshan Khatri, Ick Soo Kim

12. Nanofibers and Biofilm in Materials Science

In this chapter biofilms are introduced. Also their relationship with nanofibers is described from the viewpoint of materials science. To start, the background information for this topic is presented and explained. Also we show how biofilm causes industrial problems. The relationships of biofilms to nanofibers are classified in two main ways. One of them is the bacterial nanofiber which they produce by themselves. The other refers to the role of the fibers. A fiber seems to control the shape of biofilms which the aggregation of bacteria could produce. On the other hand, another fiber could play an important role for the attachment of bacteria onto material surfaces. Therefore, all of the mentioned examples would lead to the surface phenomena occurring on material surfaces. Finally, we present and describe a polymer brush coating as a countermeasure against biofilm formation.

Hideyuki Kanematsu, Dana M. Barry, Hajime Ikegai, Yoshimitsu Mizunoe, Michiko Yoshitake

13. Cellulose Nanofibers: Fabrication and Surface Functionalization Techniques

Cellulose fibers which consist of a bundle of stretched cellulose chain molecules with cellulose fibril are the smallest structural unit of plant fiber. These elementary fibrils or nanofibers are about 2–20 nm in diameter and a few micrometers in length. Cellulose nanofiber (CNF) is the world’s most advanced bio-nanomaterial. As the cellulose is the most abundant, renewable, and sustainable biopolymer on earth, it creates low environmental impact in its production and disposal. In this chapter, the unique properties of CNFs were introduced including stiffness, biodegradability, biocompatibility, and ability to form a strong entangled nanoporous network, thermal properties, and swelling in water and water absorptivity. Different fabrication techniques including physical methods (e.g., mechanical refining), chemical methods (treatment with acids and alkalis), and biological methods (treatment with specific bacteria and enzymes) were discussed. The chemical grafting on the CNFs and deposition of nanoparticles on nanofiber surface were described. Finally, the future prospects and challenges of CNFs were presented.

Kai Zhang, Ahmed Barhoum, Chen Xiaoqing, Haoyi Li, Pieter Samyn

14. A Broad Family of Carbon Nanomaterials: Classification, Properties, Synthesis, and Emerging Applications

Advantages of carbon-based nanomaterials with different nanostructures as (Nanodiamonds, Carbon Quantum Dots, Fullerenes Nanostructures, graphene nanosheets, carbon nanofibers and carbon nanotubes), in the studies scheme of fabrication, functionalization, potential properties and applications including electronics, biological and energy applications are discussed in the current chapter. The reported classification, properties, synthesis, properties and emerging applications of these carbon nanomaterials have opened up new chances toward the future devices and materials. A better understanding of the key factors through the knowledge founded in this work can affect the future research directions.

Ahmed Barhoum, Soliman I. El-Hout, Gomaa A. M. Ali, Esraa Samy Abu Serea, Ahmed H. Ibrahim, Kaushik Pal, Ahmed Esmail Shalan, Sabah M. Abdelbasir

15. Characterization and Evaluation of Nanofiber Materials

Characterization of nanofiber is performed to correlate test metrics with the practical characteristics of the material and to ensure reliable high quality of the products during production. The aim of single-fiber measurement procedure is to find fundamental information to better understand the relationship between the structure and the features of nanofibers. Theoretically, several characterization techniques have been utilized with nanofibers. Nevertheless, it must be borne in mind that morphology, molecular structure and mechanical properties are the most critical features of nanofibers. Therefore, in this chapter, it is attempted to explain briefly the nanofiber characterization techniques by focusing on the morphological and mechanical properties of nanofibers to provide fundamental data for evaluation of nanofiber materials.

Taha Roodbar Shojaei, Abdollah Hajalilou, Meisam Tabatabaei, Hossein Mobli, Mortaza Aghbashlo

16. Optical Spectroscopy for Characterization of Metal Oxide Nanofibers

Optical spectroscopy methods are powerful nondestructive analytical methods for investigating electronic and optical properties of materials. Due to unique properties of metal oxide nanofibers, optical methods can provide important information about fundamental properties of metal oxide nanofibers, influence of structural properties to the optical and electronic ones, and applications of metal oxide nanofibers. Optical methods involve different techniques, using light from UV-Vis-IR regions and involving different parts of the materials (free electrons, ions, etc.) into interaction with light.This chapter is dedicated to the characterization of metal oxide nanofibers using diffuse reflectance, photoluminescence, and Raman and Fourier transform infrared (FTIR) spectroscopy. General principles of these methods will be described. Calculation of the main fundamental parameters (band gap, defect levels, emission bands, etc.) will be discussed. Influence of structure parameters (such as nanofibers dimensions, chemical composition, dopants, etc.) on optical properties of metal oxide nanostructures will be demonstrated. Possible perspectives of applications of metal oxide nanofibers in optical devices will be shown.

Roman Viter, Igor Iatsunskyi

17. Electrical Properties of Nanowires and Nanofibers

This chapter focuses on the electrical properties of nanowires, nanofibers, and nanotubes made from a variety of materials. First a short review of their morphologies and composition is presented, emphasizing the wide variety of elements and compounds able to be fabricated as long-aspect ratio nanomaterials. Research of nanowires and nanofibers indicates that depending on their composition and dimensions, they can either be insulating, semiconducting, metallic, or superconducting. Several interesting effects appearing at nanoscale are discussed, among which proximity-induced superconductivity in wires made of nonsuperconducting materials due to superconducting electrodes, a switch in electrical behavior from metallic to semiconducting with chirality of carbon nanotubes, and metallicity of one-dimensional materials confined inside nanotubes that are semiconducting in bulk. Due to their small dimensions, nanowires and nanofibers present new challenges regarding their electrical properties. Small amounts of bending strains induce a semiconductor-metal transition in small diameter semiconducting nanowires. Their encapsulation in stronger nanotubes offers advantages, such as increase their mechanical strength and protect them from interacting with the atmosphere. Some materials fabricated as nanowires, while nonsuperconducting in bulk form, show superconductivity only on the nanowire surface. Last but not least, the toxic effects on humans due to handling nanowires and nanofibers are emphasized.

Cristina Buzea, Ivan Pacheco

Technologies, Emerging Applications, and Future Markets


18. Electrospun Nanofibrous Scaffolds: A Versatile Therapeutic Tool for Cancer Management

According to WHO cancer is the leading cause of mortality and morbidity worldwide with 8.2 million cancer-related deaths in 2012. Nanotechnology deals with creating a new and targeted platform for cancer therapy and diagnostics. Similar to nanoparticle-mediated drug delivery and diagnostic methods nanofibers are also being used for the same purpose. The advantages of using nanofibers are the high loading capacity, large surface area, porosity, biodegradability, cost effective, delivery of multi-model therapeutics etc. One of the most important methods for the synthesis of nanofibers is electrospinning which is based on the stretching of melt solution by electrostatic forces. Similar to the applications in reconstructive surgery and regenerative medicine, nanofibers can be used in cancer diagnostics and therapy. Researchers are trying to develop biosensors using nanofibers which can amplify the signals, improve sensitivity and accuracy of assays. Isolation and detection of circulating tumor cells (CTC) using cell capture based on nanofibers are also under development. Targeted and implantable devices for delivering bioactive components, tissue engineering and magnetic hyperthermia based intelligent nanofiber scaffolds are used in cancer treatment and management. 3D cultures of cancer cells on scaffolds have vital applications in tumor biology as well as anticancer drug screening and development whereas 3D culture and differentiation of Mesenchymal Stem Cells (MSC) on scaffolds have application in cancer surgery and wound healing.

Preethi Gopalakrishnan Usha, Maya Sreeranganathan, Unnikrishnan Babukuttan Sheela, Sreelekha Therakathinal Thankappan Nair

19. Application of Nanofibers in Ophthalmic Tissue Engineering

This chapter describes recently designed and developed nanofiber scaffolds used for ophthalmic tissue engineering applications. In recent decades, ophthalmic diseases have been a significant health concern throughout the world, and the prevalence is likely to increase, especially in developing countries. Many types of research have focused on ophthalmic disease remedies, as well as corneal transplantation, retinal detachment, and preparation of an appropriate system for regeneration of the cornea and retina by use of scaffolds. Therefore, a necessary property for scaffold materials—in addition to biocompatibility, mechanical strength, and permeability to glucose and other nutrients—is the ability to encourage cell adhesion, which could allow artificial scaffolds to be fixed in place. However, the topography of materials has an significant effect on their applications, particularly in ophthalmic tissue engineering. Recently, nanofibers have attracted attention because of their unique properties for preparation of biodegradable and nonbiodegradable scaffolds. Electrospinning is a method used to produce biocompatible scaffolds from nanofibers for the purpose of tissue regeneration. Nanofibers can produce three-dimensional scaffolds for various purposes in ophthalmic applications such as corneal transplantation and retinal regeneration.

Davood Kharaghani, Muhammad Qamar Khan, Ick Soo Kim

20. Nanofibrous Scaffolds for Tissue Engineering Application

Regeneration of damaged or malfunctioning tissues or organs is important goal of tissue engineering. Various techniques such as cell sheet engineering, cell spheroids, scaffold assisted methods and 3D printing of the cells with polymers have been tested in tissue engineering. Among these techniques, scaffold assisted method is extensively employed as it acts as a supporting matrix for the cells, providing suitable microenvironment to facilitate the cell attachment, proliferation and differentiation. In this context, designing scaffolds which mimics extracellular matrix (ECM) is essential to regenerate the damaged tissues and organs. The electrospinning technique is a versatile tool to fabricate ECM mimicking scaffolds. ECMs obtained using this technique are highly desired due to their excellent physical properties such as high surface area. High surface area assists in immobilizing bulk quantity of biomolecules like growth factors, enzymes, and drugs which provide favorable microenvironment to cells. Hence, the electrospinning is a suitable tool in regenerative tissue engineering. This chapter discusses about the importance of electrospun polymer fibers for regeneration of various tissues including bone, cartilage, heart muscles, liver and neural tissues. Influence of properties such as surface chemistry, mechanical properties and porosity on gene expression of stem cell will be addressed. The impact of biomolecule immobilization, electrospun fiber size, fiber orientation and fiber morphology on stem cell differentiation is also discussed. The performance of biopolymer and synthetic degradable polymer based electrospun fibers in tissue engineering will also be briefly reported.

Sakthivel Nagarajan, S. Narayana Kalkura, Sebastien Balme, Celine Pochat Bohatier, Philippe Miele, Mikhael Bechelany

21. Structural Multifunctional Nanofibers and Their Emerging Applications

Nanofibers are an exciting new class of nanomaterials (NMs) produced by using innovative manufacturing process technologies. Nanofibers are developed from a wide variety of materials of diverse architecture and nature. Nanofibers are divided into the following classes: (1) based on the raw material, nanofibers are classified into organic, inorganic, and carbon and composite fibers, and (2) based on the structure, nanofibers are divided into nonporous, mesoporous, hollow, and core-shell fibers. The geometrical shape (structure) of the fiber materials can be tuned from the non-woven web, yarn, to bulk structures using nanofiber fabrication techniques. Nanofibers have been widely used in a range of applications, such as energy generation, production, and storage, environmental protection and improvement, tissue engineering, pharmaceutical, and biomedical applications. This chapter discusses the nanofibers’ types, structures, fabrication techniques, inherent properties, and how these properties affect their potential usage.

Dalapathi Gugulothu, Ahmed Barhoum, Syed Muzammil Afzal, Banoth Venkateshwarlu, Hassan Uludag

22. Advances in Nanofibers for Antimicrobial Drug Delivery

Microbial infections are a major threat to public health and a leading cause of death worldwide. New strains of pathogens, such as resistant strains of viruses, bacteria, pathogenic fungi, and protozoa, are causing serious concern. Conventional antimicrobial agents have not shown therapeutic efficacy against multidrug-resistant strains of these pathogens. This review introduces the most popular applications of nanofibers in antimicrobial drug delivery for infectious diseases. Recent investigations of microbial infections, microbial resistance, and the mechanisms of antimicrobial drug resistance are discussed. Furthermore, current developments and future challenges in nanofiber technologies and applications for effective antimicrobial treatment are addressed.

Rahimeh Rasouli, Ahmed Barhoum

23. Functional Nanofiber for Drug Delivery Applications

Electrospinning is an appropriate process to fabricate nanofibers for various applications. Regarding the intrinsically high surface-to-volume ratio of electrospun fibers, they are suitable candidates for drug loading with enhanced mass transfer properties. The diverse therapeutic agents, e.g., proteins, DNA, RNA, as well as chemical drugs, could be incorporated to the nanofibers. By controlling the nanofiber morphologies, its type, and drug incorporating methods, the preferred drug release and diffusion can be adjusted depending on the intended application. In this chapter, an attempt is made to cover the most usable methods to incorporate the therapeutic agents into the nanofibers and investigate the release mechanisms, factors, and methods to control the drug releasing rate. Most usable polymeric materials to fabricate fiber-based drug delivery formulations will also be introduced.

Rana Imani, Maryam Yousefzadeh, Shirin Nour

24. Nanofibers for Medical Diagnosis and Therapy

Nanofibers are fibers having dimensions in the nanometric range of few tens to 1000 nm. Advantages of nanofibers include their high surface-area-to-volume ratio resulting in enhanced drug solubility, high porosity, superior mechanical strength, versatile surface functionalization, and similarity to the extracellular matrix which promotes their use as wound dressings. Nanofibers have demonstrated their biomedical prowess in the fields of diagnosis as well as therapy. Nanofibers have been explored as ultrasensitive biosensors for point-of-care diagnosis of cancer, detection of circulating tumor cells in cancer patients, diagnosis of malaria, and detection of urea, glucose, cholesterol, bacteria, etc. Their huge surface area offers large number of binding sites thus endowing them with the capability for ultrasensitive detection. Nanofibers have also exhibited promising potential as drug delivery carriers and as wound dressings. Smart nanofibers which release the drug in response to stimuli such as pH, temperature, magnetic field, ultrasound waves, enzyme, and light have been studied to cater to the need for on-demand drug release systems. Nanofibers for photodynamic therapy have also been reported. Multifunctional nanofibers have also been developed for combined hyperthermia and therapy. Nanofibers may be fabricated using natural or synthetic polymers and using synthetic drugs as well as herbal molecules and extracts. Drug release from nanofibers can be modified based on the choice of polymer and the method of drug loading. Nanofibers have been developed for administration through various routes such as oral, oromucosal, periodontal, transdermal, intravenous, ophthalmic, vaginal, etc. The chapter showcases the potential applications of nanofibers in medical diagnosis and therapy.

Priyanka Prabhu

25. Nanofiber Electrodes for Biosensors

Nanoscience and nanotechnology impact our lives in many ways, and the production of engineered nanofibers represents a scientific breakthrough in material design and the development of new consumer products from electronics, aerospace, automobile, photonic devices, and biosensors to renewable energy materials that are expected to impact almost every industrial and manufacturing sector, including biomedicine and biotechnology (vascular, neural, bone, cartilage, and tendon/ligament tissue engineering) and electrochemical energy storage because of their excellent conductivities, extremely large surface areas, and structural stability. Among the reported functionalities, nanofiber electrodes are popularly used as biosensors and have been extensively investigated due to their importance in solving the challenges in bioanalytical problems including clinical application, health care, chemical and biological analysis, environmental monitoring, and food processing industries. Graphene, graphene oxide, chemically reduced graphene oxide, carbon nanotubes (CNTs), diamond, carbon nanofibers (CNFs), ZnO nanofibers, conductive polymers (like polypyrrole, polyaniline, polythiophene nanofibers), Pt–Au nanoparticle-decorated titania nanotube array, boron-doped diamond nanorods, and gold nanofiber electrodes are some of the biosensing materials used for DNA biosensor, glucose biosensor, electrochemical biosensors, or electrocatalytic biosensor, respectively. Carbon-based materials such as diamond and carbon nanofibers are highly important for the construction of practical nanoscale sensing devices and systems because of high degree of chemical stability, their relatively wide potential windows in aqueous media, good biocompatibility, low cost, and relative chemical inertness in most electrolyte solutions. Innovation and research in the field of nanofibers is paving way for a new era in biosensing application.

Subhash Singh

26. Nanofibers for Medical Textiles

This chapter introduces the nanofibers for medical textiles. Nanofibers possess the various unique characteristics, which enable them to be used for different fields of advanced textiles. The structure of nanofibersNanofibers for MedtechMedtech, nanofibers for plays an important role to achieve the functional applications for technical medical textiles (Medtech). The key formation mechanisms of structured functional nanofibers such as core-shell, aligned, porous, composite, tubular, mechanical, and chemical are reviewed, including the briefed information on the processes involved. Recently, many researchers are focusing on nanofibers as the suitable methods and materials for Medtech which enhance the scope of medical textiles. Biocompatibility, biodegradability, and mechanical properties are the main issues for biomedical textile products as scaffolds. To overcome these issues, electrospun nanofibers could be very suitable for medical textiles, because the electrospun nanofibers are continuous nanofibers meshes that mimic the extracellular matrix as the medical textiles product. The main features of advanced examples and innovative applications are reviewed, and at the end of this chapter, the future of medical textiles is also discussed.

Muhammad Qamar Khan, Davood Kharaghani, Zeeshan Khatri, Ick Soo Kim

27. Recent Trends in Nanofiber-Based Anticorrosion Coatings

Various forms of polymer coatings have been applied in corrosion-control attempts to prolong the useful life of materials. The drawback of polymer coating systems, however, is the inability to function if the coating is damaged or breached. A design for self-healing coatings that would provide repetitive protection has recently been proposed. Self-healing is a natural ability found in both humans and animals to spontaneously cure injury or illness, and the ability is now being used in anticorrosion coating. This chapter begins with brief descriptions of corrosion and corrosion protection. That is followed by descriptions of the properties of various anticorrosion coatings, the concept of self-healing coatings, and the nanomaterials that are used in self-healing coatings. Then, the use of nanofibers as an important nanomaterial in the self-healing process is explained as follows. The network structure by nanofibers in a coating system not only provides a container for inhibitors but also provides channels and pathways for the release of corrosion inhibitor. The performance of a self-healing coating that uses nanofibers is determined by the successful release of corrosion inhibitor. The controlled release of corrosion inhibitors via a change in the pH of nanofibers enhances the performance of self-healing coatings. Finally, trends are proposed for the use of nanofibers as self-healing, anticorrosion coatings.

Akihiro Yabuki, Indra W. Fathona

28. Nanofibers for Membrane Applications

Electrospun nanofiber membranes (ENMs) are the next-generation materials that offer solutions to global issues in diverse applications including health, energy, and environmental applications. Polymeric nanofibers fabricated via electrospinning can be used effectively for environmental remediation due to its light weight, high surface area, and interconnected porous structure. The controlled pore size and high porosity of the ENM offer enhanced structural performance, while the high surface-to-volume ratio enriches the functional reactive sites. This chapter gives an overview of the methods of fabricating ENMs with regard to structural, surface, and functional properties for water and liquid applications. Several membrane patterns including two- or three-layered composite membranes, mixed matrix membranes, thin-film nanocomposites, and metal-organic membranes using different materials, methods, and arrangements of nanofibers have been demonstrated for different water/liquid applications, including microfiltration, ultrafiltration, nanofiltration, reverse osmosis, oil/water separation, membrane distillation, and bio-separation.

Anbharasi Vanangamudi, Xing Yang, Mikel C. Duke, Ludovic F. Dumée

29. Electrospun Membranes for Airborne Contaminants Capture

This chapter presents an overview of nanofiber-based materials fabricated for applications in air filtration. Air contaminants can be classified as gaseous or particulate matter, and the capability to capture these will strongly vary with the specifics of their chemistry, morphology, and agglomeration kinetics, as well as with atmospheric conditions, such as humidity and temperature. The capture mechanisms of different design methods must therefore be adapted to achieve stringent capture efficiency targets. For one, the benefits of nanofibers over more conventional microfibers reside in the small fiber diameter facilitating more tuneable and finer pore sizes, narrower pore size distributions, and higher specific surface areas. The advantages of nanofiber media for filtration applications, such as extreme compactness, are highlighted in the chapter concerned with the specific properties of nanofiber filters. The challenges arising from the use of nanofibers that is contrasted by opportunities that may direct future trends of nanofiber filters for air filtration applications are discussed at the end of the chapter.

Riyadh Al-Attabi, Y. S. Morsi, Jürg A. Schütz, Ludovic F. Dumée

30. Design of Heterogeneities and Interfaces with Nanofibers in Fuel Cell Membranes

Many fuel cell membranes are highly heterogeneous systems comprising mechanical and chemical reinforcing components, including porous polymer sheets, nanofibers or nanoparticles, as well as radical scavengers or hydrogen peroxide decomposition catalysts. In the last 10 years, great attention has been devoted to 1D nanomaterials obtained by electrospinning. Several chemistries and compositions from aliphatic or aromatic polymers to metal oxides and phosphates and morphologies from nanofibers to nanotubes have been employed to prepare nanocomposite membranes. Despite the significant advances realized, further improvements in ionomer membrane durability under operation are still required. In particular, it is crucial to control the heterogeneity induced by the nanofiber component and to strengthen the interface between them and the matrix. Specific interactions have been demonstrated to improve the fiber/matrix interface with overall improvement of dimensional and mechanical properties. In this chapter we review the different approaches to fuel cell membrane reinforcement based on electrospun polymers and inorganic nanofibers.

Marta Zatoń, Sara Cavaliere, Deborah J. Jones, Jacques Rozière

31. Nanofibers as Promising Materials for New Generations of Solar Cells

Various applications of nanotechnology have been intended to approach enhanced and efficient solar cell devices with more economically pathways. Effective systems for conversion cost, efficient solar energy storage systems, or solar energy on a large scale are created by efficient solar cells which improved using nanofiber (NF) materials. This chapter provides an overview of photovoltaic and solar cell devices (i.e., dye sensitize solar cells, organic solar cells, and perovskite solar cells) based on nanofibers (NFs) as a key element. Details about the main types of solar cells and their working principles and how engineered NFs are used for solar cells are discussed. The potential application of the three representative NF materials, i.e., metals and metal oxides, carbon, and conductive polymers, were reviewed. The future development of NFs toward next-generation solar cells is finally summarized.

Ahmed Esmail Shalan, Ahmed Barhoum, Ahmed Mourtada Elseman, Mohamed Mohamed Rashad, Mónica Lira-Cantú

32. Nanofibers for Water Treatment

Water colorization has raised a worldwide health and environmental concern due to the impact of dyes on marine and river organisms. The volume of nonrecycled dyes discarded varies depending on the dye/fabric affinity, but is for instance estimated to reach up to 40% of the total dyeing volume for reactive dyeing of cellulose. In addition, the large majority of the dyeing facilities are remotely located and operating into emerging economies where water treatment processes are limited, further increasing pressure and damage on already pollution-stressed ecosystems. Dye pollutants cover a category of organic molecules with different molecular structures, hence biodegradability, yet their composition often includes multiple aromatic rings and trace heavy metals, as well as other toxic and potential carcinogen compounds such as azoic groups. Adsorption is a promising technique to limit the release of dyes and partially degraded dyes in the environment, while reversible adsorption offers the possibility to recycle wasted dyes for reuse, hence minimizing the pollution load. As opposed to other separation techniques, adsorption, typically performed with activated carbons, offers opportunities to combine low operation cost with high performance as well as fast kinetics of capture if custom-designed with the right choice of adsorbent structure and surface chemistry. Nanofibers possess a higher surface to volume ratio compared to commercial macro-adsorbents and a higher stability in water than other nanostructures such as nanoparticles. This chapter comprehensively reviews the performance of nanofiber materials against benchmark commercial and recognized adsorbents for basic, acid, direct, and reactive ionic dyes adsorption. The discussion further investigates the impact of fibers morphology and composition on their adsorption capacity and proposes routes toward rationale design of cost-effective nanofiber-based adsorbents.

Elise des Ligneris, Lingxue Kong, Ludovic F. Dumée

33. Engineering Nanofibers as Electrode and Membrane Materials for Batteries, Supercapacitors, and Fuel Cells

Energy and environment are two major problems facing mankind today. Developing environment-friendly and energy-saving technology has always been the focuses of researchers all over the world. Batteries, supercapacitors, and fuel cells are three widely used or promising devices that can ease the energy and environmental pressures. However, there are still many problems and deficiencies that need to be solved or improved, such as low capacity, low-power density, and poor durability. In order to address these drawbacks, nanofibers are introduced into the application of electrode and electrolyte fabrication because of the high specific surface area, interpenetrating network, and strength. This section will introduce the applications of nanofibers in batteries, supercapacitors, and fuel cells in detail.

Liu Haichao, Haoyi Li, Mahmoud Mohammed Bubakir, Weimin Yang, Ahmed Barhoum

34. Emerging Applications of Cellulose Nanofibers

Cellulose is the most abundant biopolymer on Earth. In addition, it is renewable, biodegradable, and relatively cheap. Cellulose nanofibers (CNFs) have been produced most commonly from plants, algae, and bacteria. They can be isolated, e.g., from wood-derived fibers that have been microrefined to microlevel and even to nanolevel. In this chapter, we comprehensively review the unique properties and emerging applications of CNFs. We anticipate that CNFs as a new environmentally friendly material will be widely used in many areas such as reinforcement of polymers, energy production and energy storage, environmental protection and improvement, and healthcare. Therefore, there is a necessary to do more research on the potential emerging applications of CNFs.

Ahmed Barhoum, Haoyi Li, Mingjun Chen, Lisheng Cheng, Weimin Yang, Alain Dufresne


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