1.1 Introduction

Originally, textiles/clothing relates to catering the needs for protecting the human body from cold, heat, and sun. A more comprehensive definition of conventional textiles also include home textiles utilized in furnishing and the ones that find use in the bedroom and the bathroom [1, 2]. Following these basic needs, aesthetics have become one of the main drivers for people to use clothing and textiles [3]. Recently, more functionality has started to be required, so functional textiles/technical textiles, which can cater more sophisticated needs, have emerged. The last generation of textiles, smart textiles, is capable of one step ahead: sensing and reacting to environmental stimuli [2, 4, 5].

Smart textiles can be also named as “intelligent,” “stimuli-sensitive,” or “environmentally responsive” [6]. Smart textiles have been described as “fibers and filaments, yarns together with woven, knitted or non-woven structures, which can interact with the environment/user” [7, p. 11958]. Smart textiles have broadened the functionality and, consequently, application areas of conventional textiles [7], as they show promise for use in various applications including biomedicine, protection and safety, defense, aerospace, energy storage and harvesting, fashion, sports, recreation, and wireless communication [4, 8–10].

Smart textile components perform various functions such as sensing, data processing, communicating, accumulating energy, and actuating as shown in Figure 1.1 [11]. In these fields, textile structures present some advantages such as conformability to human body at rest and in motion, comfort in close contact to skin, and suitability as substrates for smart components [8].

“Smartness” refers to the ability to sense and react to external stimuli [6]. The stimulus of interest can be electrical, mechanical, chemical, thermal, magnetic, or light [4, 12]. Smart systems offer the capability of sensing and responding to environmental stimuli, preferably in a “reversible” manner, that is, they return to their original state once the stimulus is “off” [6].

Smart textiles can act in many ways for vast purposes including releasing medication in a predetermined way, monitoring health variables, following pregnancy parameters [13], aiding physical rehabilitation [14], regulating body temperature, promoting wound healing [15], facilitating tissue engineering applications [16], photocatalytic stain removing [17], preventing flame formation [18], absorbing microwaves [19], interfering with electromagnetic radiation [20], wireless communicating between persons, between person and device, and between devices (as in the case of IoT), and harvesting and storing energy [10]. In an everyday example, the smart textiles used for fashion, kids’ toys, or entertainment can change color, illuminate, and display images and even animations [4, 10].

Smart textiles have attracted international research interest as reflected in the programs of the international funding bodies, for example, “Wear Sustain,” a project funded by the European Commission. The Wear Sustain Project is directed by seven organizations, both public and private entities, across Europe, including universities, research centers, and short- and middle-scale enterprises (SMEs). This project has launched 2.4 million euros for funding teams to develop prototypes of next-generation smart textiles [21]. US-based National Science Foundation grants $218,000 to a career project titled Internet of Wearable E-Textiles for Telemedicine [22]. NSF of the USA has invested more than $30 million on projects studying smart wearables. The projects include belly bands tracking pregnancy variables, wearables alerting baby sleep apnea, and sutures that collect diagnostic data in real time wirelessly. NSF also supports the Nanosystems Engineering Research Center (NERC) for Advanced Systems for Integrated Sensors and Technologies (ASSIST) at North Carolina State University working on nanotechnological wearable sensors [23].

Different components are used for imparting smartness into textiles. These components include conductive fibers, conductive polymers, conductive inks/dyes, metallic alloys, optical fibers, environment-responsive hydrogels, phase change materials, and shape memory materials. These components are utilized in forming sensors as well as electrical conductors, and connection and data transmission elements [4]. Conductive materials added to fibers/yarns/fabrics include conductive polymers, carbon nanotubes, carbon nanofibers, or metallic nanoparticles [4, 24–26].

“Smartness” can be incorporated into textiles at different production/treatment steps including spinning weaving [27], knitting [28], braiding [29], nonwoven production [30], sewing [31], embroidering [3], coating/laminating [32], and printing [33] as shown in Figure 1.2.

Conventionally, conductive fibers and yarns are produced through adding conductive materials to fibers, or via incorporation of metallic wires/fibers such as stainless steel or other metal alloys [4, 25]. Another way to produce smart textiles is through incorporation of conductive yarns in fabrics, for example, by weaving. Drawbacks related with this method are the complexity, non-uniformity, as well as difficulty in maintaining comfortable textile properties [7].

Nanotechnology has carried the level of smart textiles one step further. Via application of nanosized components, textile materials receive smart functionalities without deteriorating textile characteristics [10, 34]. Consequently, functions conventionally presented by nonflexible rigid bulk electronic products are achieved by “clothes” [2].

Smart wearables should present capability of recognizing the state of the wearer and/or his/her surrounding. Based on the received stimulus, the smart system processes the input and consequently adjusts its state/functionality or present predetermined properties. Smart textiles should also cater needs regarding wearability [7]. Via incorporation of nanotechnology, the clothing itself becomes the sensor, while maintaining a reasonable cost, durability, fashionability, and comfort [35].

Based on their “smartness” level, smart textiles may be investigated under three categories [33]:

• – Passive smart textiles
• – Active smart textiles
• – Very active smart textiles.

The first group can only detect environmental stimuli (sensor), whereas the second group senses and reacts to environmental stimuli (sensor plus actuator). On the other hand, the third group senses and reacts to environmental stimuli, and additionally adapts themselves based on the circumstances (sensor, actuator, and controlling unit) [2, 4].

1.2 Nanofibers

Among various forms that nanomaterials can take such as nanorods, nanospheres, and so on, the fiber form comes to the forefront due to its superior characteristics. The advantageous properties of this material form include flexibility, high specific surface area, and superior directional performance. These merits allow many uses from conventional clothing to reinforcement applications in aerospace vehicles. Nanofibers refer to solid state linear nanomaterials, which are flexible and have aspect ratios exceeding 1000:1. Nanomaterials are characterized by their dimensions at least one of which should be equal to or less than 100 nm. A million times increase in flexibility can be achieved via reduction of the fiber diameter from 10 μm to 10 nm, which also leads to increases in specific surface area, and in turn surface reactivity [46].

Numerous functionalizations can be attained by use of nanofibers produced from various polymers including polypyrrole, polyaniline [7, 47], polyacetylene [4], polyvinylidene fluoride, poly N-isopropylacrylamide (PNIPAAm), polyethylene glycol, and so on, and incorporation of different functional components such as carbon nanotube, graphene, azobenzene, and montmorillonite nanoclay [10, 34, 48, 49]. More of these polymers and functional components can be found in the following chapter [46]. Via use of these nanofibers, it is possible to achieve smart functionalities as follows.

1.3 Nanosols

Nanosols are coating agents used for functionalizing textiles. Nanosols are colloidal solutions of metal oxide particles in nanoscale dimensions in water or organic solvents [61]. Nanosols include inorganic nanoparticles prepared via the sol–gel method [9, 50].

Nanosols present metastable property due to their high surface-to-volume ratio. Hence, 3D network structures can be formed of nanosols by aggregation of nanoparticles and successive solvent evaporation in course of coating [61]. Nanosols are formed through hydrolysis of a precursor material. The precursors can be inorganic metal salts or metal organic compounds such as acetylacetonate or metal alkoxides. Metal or semimetal alkoxides are commonly utilized, which turn into hydroxides via hydrolysis processes. At high concentrations, hydroxides are generally unstable; thus, they may be subjected to successive condensation reactions resulting in nanoscale particle formation. Some examples of nanosol precursors can be given as Al(OC₄H₉)₃, Si(OC₂H₅)₄, tetraethoxysilane (TEOS), and titanium (IV)isopropoxide Ti(OC₃H₇)₄ [50, 61].

Similar to other nanoscale materials, nanosols also enjoy great effectiveness based on high specific area in terms of their dimensions generally below 100 nm [61]. Accordingly, coatings prepared with nanosols exhibit thicknesses of several hundreds of nanometers [62]. Using nanosols, surface or bulk properties of different substrates such as textile materials can be altered [61]. Via application of nanosols, various functions can be imparted to textiles. These functions can be divided into four categories according to Mahltig: optical (coloration, UV, and X-ray protection), chemical (inflammability, self-cleaning), biological (antimicrobial, biocompatibility), and surface-functional (hydrophobic, hydrophilic, abrasion resistant) functions [9].

Nanosol coatings are usually prepared via the sol–gel method as mentioned before. Various solvents are used for nanosol preparation including water, isopropyl, or ethanol. It is possible to modify nanosols through simple methods resulting in a variety of functionalities. On the other hand, a shortcoming related to nanosols is limited stability caused by water if selected as the solvent [50, 62]. If proper post thermal treatment is not carried out, the applied nanosol coating will present an amorphous structure referred to as “xerogel.” Nevertheless, water is generally chosen in order to avoid undesirable aspects of organic solvents related to flammability, safety, and cost effectiveness [9, 63].

An important aspect related with nanosol applications on textiles is the adhesion between nanosol coating and the textile substrate. This is especially problematic with synthetic-fiber textiles. In order to increase adhesion, various techniques are utilized including use of cross-linkers, applying thermal, plasma, and corona treatments to activate the mentioned surfaces [61].

1.4 Responsive Polymers

Smart textiles are generally considered as textiles with miniaturized electronic devices integrated within [4]. This definition is not false, but it is incomplete. Apart from electrically conductive materials, some polymers show responses triggered by changes in the environmental conditions including pressure, temperature, light, magnetic field, and so on [12, 64–67]. These polymers are defined as environmentally sensitive, stimuli-responsive, intelligent, or smart polymers [6]. Even though the materials are nanostructured, the responses can be observed at the macroscopic level and can be reversible [65, 66].

The response-triggering stimuli can be generally categorized as physical (temperature, pressure, electrical field, magnetic field, and ultrasound), chemical (pH, solvent composition, ion type, and ionic strength), and biological (glucose, enzyme, and antibody) [68, 69]. Nevertheless, biological stimuli can be also considered as a sub-group of chemical stimuli. Physical stimuli lead to changes in molecular interactions to a certain extent. The advantage of physical stimulus-triggered systems is the possibility of local and remote activation. Nevertheless, the systems in the human body are very closely tied to (bio)chemical processes. This makes the systems responsive to (bio)chemical stimuli including pH, ions, and biomolecules very important. There are also systems responsive to multiple stimuli. These systems are referred to as dual- or multi-responsive polymer systems [24].

The response mechanisms vary from polymer to polymer. These include neutralization of charged groups upon pH change or addition of oppositely charged chemical species, or change in the hydrogen bond strength [65]. Switchable solubility is an important mechanism of smart functions. For most of the smart polymers, a critical point can be mentioned where the response, that is, the change in polymer’s property, is observed [6, 66].

Among different environmentally responsive polymers, poly(N-isopropylacrylamide) (PNIPAAm) and its derivatives attract extensive interest. PNIPAAm solutions show reversible thermo-responsive solubility behavior. They present soluble characteristic below a specific temperature, called as lower critical solution temperature (LCST), and insoluble characteristic over this point [24]. Some monomers used in preparation of environmentally responsive polymers include hydroxyethyl methacrylate (HEMA), vinyl acetate, acrylic acid, and ethylene glycol [6].

By incorporation of nonsoluble components, solubility behavior of polymers can be manipulated. Nanoscale dimensions show promise for environmentally responsive polymers in terms of response rate in comparison to bulk materials based on higher surface area. Thus, polymer systems with different smart functionality, response mechanism, and rate can be attained through sound design of components and architecture. Systems responsive to different stimuli can be fabricated from different precursor materials [12].

When smart polymers are the subject, one thinks that these are highly engineered, advanced materials produced via sophisticated synthesis routes starting from chemical precursor species. However, there are also environmentally responsive polymers based on natural materials beside synthetic ones, as well as hybrid ones that contain synthetic and natural components together. The natural components that find use in environmentally responsive polymers include proteins (collagen, gelatin) and polysaccharides (chitosan and alginate) [6].

There are many ways in production of environmentally responsive polymers including physical cross-linking methods (heating/cooling, ionic interaction, complex coacervation, H-bonding, maturation, cryogelation) [70], chemical cross-linking methods (chemical grafting, radiation grafting) [6], and advanced techniques such as sliding cross-linking, double networks, and self-assembling from genetically engineered block copolymers [64]. In the fourth chapter [24], more insight into responsive polymers is given.

1.5 Nanowires

Nanowires present high aspect ratios with diameters at the nanoscale (5–100 nm), whereas the lengths are between 100 nm and several microns [71]. In comparison to nanoparticles in other shapes like nanospheres and nanorods, nanowires exhibit some advantages based on their high aspect ratios. These advantages include effective electrical and thermal conductivity as well as mechanical flexibility [8]. On the other hand, nanoscale diameters of nanowires offer advantages in obtaining transparency from the final product [71].

Nanowires, similar to other nanomaterials, offer some advantages over bulk counterparts. As an example, Si nanowires present high signal-to-noise ratios and ultra-high sensitivities compared to conventional materials that allow use for detecting single virus particles, analyte presence, and DNA sequencing [72]. The shape of nanowires provides a direct pathway for electrical transmission lowering resistance. This shape allows orientation easier compared to other shapes. Metal nanowires may be superior to carbon nanotubes, which show high resistance at junctures [8].

Nanowires are made of metals, metal oxides, conductive polymers, or semiconductor materials. Different metals can be used in nanowire preparation including silver, gold, and copper, among others. Conducting polymers can be named as polyaniline, polythiophene, poly(p-phenylenevinylene), and polypyrrole. Semiconducting materials include oxides (ZnO, CuO, SnO₂), sulfides (Cu₇S₄, CoS₂), and others (Si, ZnSe, CdTe, …). Semiconductive silicon nanowires have been used for preparing biosensors [8, 73]. Among oxide semiconductors, ZnO is heavily investigated, the conductivity of which can be controlled via addition of dopants from insulating to highly conductive levels. The conductivity and other properties can be fine-tuned via manipulating the chemical composition. Miniaturized electrical devices including resistors, transistors, diodes, logic gates, and similar devices have been produced via use of nanowires on rigid and flexible substrates [8, 71].

Based on flexibility, in terms of precursor materials as well as resultant properties, nanowires show promise for use in fabrication of nanoelectronics, optoelectronics, electrochemical, and electromechanical devices [8]. Nanowires have been investigated for use in molecular chemical and biological sensors [74, 75], nanodrug delivery systems [76], personal thermal management, photocatalysis, strain sensors, lithium batteries, photodetectors, supercapacitors, and nanogenerators [8, 10]. Nanowires can be treated in solutions and mounted on numerous substrates under moderate conditions. Thus, nanowires can be exploited for preparation of minidevices that provide high-quality service over high surface areas, which just suits textile usage [77]. For more information on nanowires, Chapter 5 [8] can be reviewed.

1.6 Nanogenerators

Power-generating components supply electrical energy in smart textiles, which can be used for activation of smart functions and wearables such as MP3 players integrated in textiles, as well as charging other appliances including cell phones. Energy harvesting is an interesting field where smart nanotextiles can be used. Even though notable advancement has been attained regarding use of lithium rechargeable batteries, use of them in smart textiles poses challenges based on durability and comfort requirements [8]. Power generation may be achieved by collecting the energy dissipated by the body of the wearer as well as from the surrounding nature [5, 10, 40].

A number of functions can be obtained from smart textile devices. Yet the response mechanism needs energy to be activated. The selection of an appropriate energy source for smart textiles still remains an unsolved question. Conventional batteries need frequent replacement/recharge, so their use is not very practical. Additionally, they cannot cater the light weight, flexibility, safety, and energy density performance required for common textile use [40]. Many studies have been conducted to develop suitable power devices like batteries or supercapacitors that can be integrated into textiles. Based on the shortcomings of batteries, novel types of energy-harvesting devices have been developed. These devices have the capability to convert environmental energies into electricity. The mentioned environmental energy resources include sunlight, body thermal energy, and mechanical energies (human motion, heartbeat, wind, wave, tide, sound) [8, 10, 40, 78].

Various solar cells have been developed to generate electricity from solar energy, including novel ones that are flexible and can be integrated into textiles. The limitations of solar cells stem from high dependency on weather, location, and season that do not allow sustainable supply of power [10, 39].

As one can expect, thermoelectric nanogenerators can produce electricity from thermal energy in the presence of a temperature gradient. In these devices, solid-state p- and n-type semiconducting materials are utilized. Unfortunately, the output and efficiency of thermoelectric nanogenerators are not sufficient for use in smart textiles [10, 78].

Compared with other power sources, devices that produce electricity from mechanical motions exhibit advantages. Mechanical energy sources can be the wearer (human motion, heartbeat) or the environment (wind, wave). These types of nanogenerators can be studied in two classes: piezoelectric nanogenerators and triboelectric nanogenerators, which have been extensively investigated [10, 40, 79]. Li et al. [79] produced a triboelectric nanogenerator using poly(vinylidene fluoride) nanofibrous membrane coated with polydimethylsiloxane and polyacrylonitrile nanofibers coated with polyamide.

Triboelectric nanogenerators present a very interesting type of nanogenerators. These nanogenerators function based on triboelectrification, which is generally considered as an unwanted phenomenon. Energy generation takes place as a result of triboelectrification and electrostatic induction, where flexible and stretchable materials that have everyday common use can be utilized including polyamide, polytetrafluoroethylene, and silk [46, 80]. Triboelectric nanogenerators have first been announced by Prof. Wang of Georgia Institute of Technology and his research team in 2012 [81]. With improvement of triboelectric nanogenerators via selection of ideal materials and optimized designs, area power density of 500 W/m² and total conversion efficiency rates of 85% have been achieved [82, 83].

There are also electromagnetic generators that are conventionally utilized to produce electricity from mechanical energy. However, their use in textiles is not practical based on the necessity of a heavy rigid magnet and low efficiency for low frequency movements. On the contrary, nanogenerators allow use of different materials, design flexibility, and low-frequency performance. More research on nanogenerators can be found in Chapter 6 [10].

1.7 Nanocomposites

Nanocomposites are promising for use in various areas such as automotive, aerospace, defense, and biomedicine fields. Nanocomposites allow design and characteristic choices that are impossible with conventional composites. Based on their light weight and multifunctionality, nanocomposites cater the needs without compromising aesthetics and comfort of textiles. In smart textiles, nanocomposites take part in sensors, actuators, mediators, biosensors, thermoregulation, energy storing, and harvesting elements, among others. Nanocomposites are especially promising for sophisticated niche areas. Nanocomposites have already started to be used in a number of applications; nevertheless, there are still various potential areas where nanocomposites can be utilized in the future [26].

Nanocomposites can be classified in three groups in terms of their matrices: ceramic-matrix nanocomposites, metal-matrix nanocomposites, and polymer-matrix nanocomposites [84]. Their flexibility and conformability with textiles render polymer-matrix nanocomposites more suitable for smart textile use [26]. Polymer-based nanocomposites can be manufactured through different methods such as in situ polymerization [6, 85], melt homogenization [86], electrodeposition, solution dispersion [34, 85], sol–gel technique [87], template synthesis, and some advanced methods including atomic layer deposition and self-assembly [41, 84].

To improve properties of polymers, different reinforcement elements including particles, fibers, or platelets, of the micro- or nanoscale, are utilized. The reinforcement components contribute to the strength, thermal resistance, fire-retardancy, electrical conductivity properties, and so on. When nanostructured reinforcements are used, these special properties and more can be achieved without interfering with textile performance characteristics such as flexibility, stretchability, breathability, drape, softness, hand, and others. Moreover, via use of nanosized fillers, the desired properties can be achieved at concentrations much lower compared to conventional microfillers [84, 88]. The nanocomposite components that have been studied can be given as carbon nanotubes; metals, metal oxides, and inorganic nanoparticles [88]; conducting polymers, nanocellulose; and nanoclay [89].

Among nanoreinforcing elements, carbon nanotube addition in nanocomposites results in substantial improvements in mechanical properties [84, 88], antibacterial property, and conductivity [90].

Cellulose is one of the most abundant materials on earth [91]. Besides its abundancy, cellulose also presents biodegradability, biocompatibility, and renewability [60]. In its nanostructured form, cellulose has been utilized in sensors, biosensors, self-powering devices [92], and actuators [89, 93]. Bacterial cellulose is a kind of cellulose that is excreted by bacteria rather than plants. Unlike common plant cellulose, bacterial cellulose exhibits nanostructure in its pristine form [94]. In a related example, Lv et al. [92] developed a bacterial cellulose-based nanocomposite biosensor detecting glucose level. Nanocellulose has been utilized in pH and heavy metal sensors. In these applications, detector molecules are stabilized on cellulose [93, 95]. Nanocellulose-based nanocomposites are also utilized in strain sensors and actuators. Electroactive paper is an interesting example of nanocellulose-based nanocomposite exhibiting electrical field-induced motion [26, 96].

Conducting polymer is another group of polymers used in nanocomposites. Conducting polymers exhibit inherent conductivity. Incorporation of conducting polymers results in improved dielectric, catalytic, piezoresistive, magnetic susceptibility, or energy storage and harvesting properties [84, 88]. Polyaniline, polypyrrole, and poly(3,4-ethylenedioxythiophene), as polythiophene derivatives, are conducting polymers that show promise for use in smart textiles in terms of their mechanical strength and elasticity, and durability together with electrical properties. Mechanical properties, solubility, and dispersibility characteristics of conducting polymers are not generally as good as common polymers. The resistance of polymeric materials may show change over time. Furthermore, they may need long time to respond to environmental stimuli. Thus, it is feasible to use them with nanofillers in composite form to attain desired performance properties concurrently [93, 97].

Nanoparticles of metals, metal oxides, and nonmetal oxides are utilized in nanocomposites as reinforcement components [88, 98]. These nanocomposites show unique mechanical, thermal, and electrical characteristics. Metal nanoparticles have found use in nanocomposites developed for catalyst and biomedical applications. Nanoparticles of metal oxides are added to nanocomposites to obtain mechanical strength, electrical and thermal conductivity, barrier effect, antibacterial effect, UV protection, and self-cleaning property. Among metal oxide particles, TiO₂ and SiO₂ are commonly utilized [84, 88].

Nanoclay-reinforced nanocomposites have been extensively studied in terms of their special properties including thermal resistance, flame retardancy, stiffness, and strength [26, 84]. Nanowire-based nanocomposites have found use in energy storing and harvesting applications [8]. More information on nanocomposites can be found in Chapter 7 [26].

1.8 Nanocoating

Nanocoating, that is, coating a substrate with nanosized particles, is used to develop smart wearables with advanced functions and performance. Efficient nanocoating can provide advantages in terms of comfort, durability, and aesthetics. Via nanocoating, functions including UV protection, self-cleaning, antibacterial effect, and water repellence, among other smart properties, can be imparted to textiles, at the same time maintaining textile comfort characteristics required by the wearer such as breathability, drape, etc. [4].

There are different methods including conventional means like dip coating to apply nanocoating on smart textiles [32]. Various other coating methods have been developed on textiles such as transfer printing, immersion, padding, rolling, spraying, and simultaneous exhaust dyeing. Electrostatic spinning (electrospinning) can also be considered as a means of nanocoating where a web of nanoscale fibers is coated on a surface [34]. Rinsing and padding methods are widely applied for textile applications [34]. During the padding process, metal oxide nanoparticle systems are applied on textile substrates, followed by thermal processes [61]. Via coating, in situ synthesis, cross-linking, and immobilization of nanomaterials onto textile surface are carried out [34].

An inevitable necessity for nanomaterials in terms of coating is dispersibility in colloids. van der Waals and electrostatic double-layer attractions lead to agglomeration and microcluster formation of nanoparticles. Effective dispersion can be achieved via inclusion of dispersants like surfactants, grinding thoroughly, and functionalization by adding organic monomers and compounds [34, 84].

A major issue related with nanomaterials in terms of use on textiles is durability. Because of nonexistence of functional sites, nanoparticles do not present attraction to textile materials. In order to obtain durability of the designed characteristics, chemical or physical surface functionalization methods are applied. Another option is to embed nanomaterials in polymers applied on textiles and obtain nanocomposite coatings [26, 34].

Different nanotechnology-based coating methods are applied on textiles including sol–gel method, cross-linking method, and thin-film deposition methods (physical vapor deposition, vacuum evaporation, ion implantation, and sputter coating) [34].

More insight into nanocoating techniques can be found in Chapter 8 [41].

1.9 Nanofiber Formation

As mentioned before, nanofibers present very important advantages based on their high specific surface area. There are various methods to produce nanofibers. Electrostatic spinning, which is generally referred to as electrospinning, is the most commonly used nanofiber production method [46]. Other than electrospinning, there are a number of other techniques including force spinning, phase separation, melt blowing, bicomponent spinning, flash spinning, and so on. Via these methods, nanofibers are generally obtained in the form of nanowebs in random orientation where fiber diameters may range from several nanometers to hundreds of nanometers [99].

The electrospinning technique is advantageous in terms of its simplicity and applicability to various materials such as polymers, ceramics, and metals [46, 99]. In an electrospinning setting, a capillary tip is exposed to high voltage. This leads to formation of an electrical field between that capillary tip and a grounded collector. A pendent drop is formed at the tip by the solution dope flowing through it. The shape of the drop is first turned into a hemisphere than to a cone (referred to as the Taylor cone) due to the electrical force. As the electrical force exceeds the surface tension of the polymer drop, a jet of the solution ejects toward the collector. The jet presents an instable whipping motion due to the imbalance in the electrical charge. This motion leads the jet to stretch and to attenuate. The jet rapidly dries into nanofibers, which accumulate on the collector [34, 100].

If the viscosity is not sufficient, then drops instead of fibers are obtained. Parameters affecting electrospun fibers include solution characteristics, processing variables, and ambient conditions. The solution parameters include viscosity, surface tension, conductivity, concentration, and molecular weight. Processing variables consist of flow rate, voltage, collector structure, and syringe-to-collector distance, whereas the ambient conditions refer to temperature and humidity of the surrounding air medium [101].

Nanofibers, generally produced by electrospinning, suffer from lower mechanical properties. Post-treatments have been developed to enhance the mechanical properties, including cross-linking and welding. Using higher viscosity dopes to eliminate weaker points due to solvent-rich regions has also been reported to improve nanofiber strength. Sonication may be a means to overcome this disadvantage for decreased dynamic viscosity. Another option is to introduce suitable nanofillers to the solution [46].

In addition to fiber formation, the nanofibrous mat can be concurrently coated onto a substrate. The fiber diameter can range between 10 and 500 nm based on the conditions. Nanofibers of different polymers can be obtained such as polyvinyl alcohol, polyurethane, polyamide, polyacrylonitrile, and polylactic acid via electrospinning [34].

Electrospun nanofibrous mats show high porosity and low pore dimensions. These properties are required for a number of applications like filtration systems (for water treatment, climatization, etc.) [102, 103], separators in lithium ion rechargeable batteries [104], scaffolds in tissue engineering [105], wound dressing [106], and controlled drug delivery [107].

Novel nanofiber production techniques have been developed in order to overcome shortcomings of conventional electrospinning: low production rate; consequently, difficulty in utilization in large-scale production. Those novel procedures include modified versions of electrospinning and electroless spinning methods. Modifications of the electrospinning process can be listed as multi-needle electrospinning, needleless electrospinning, bubble electrospinning, electroblowing, microfluidic-manifold electrospinning, roller electrospinning, and melt electrospinning. Nanofiber production methods without use of electrostatic force include melt blowing, template melt extrusion, force spinning, flash spinning, bicomponent spinning, phase separation, and self-assembly [99].

Among modified electrospinning processes, multi-needle electrospinning was developed to increase the production rate compared to the conventional single-needle electrospinning system, which is constrained with fiber formation from only one needle. In multi-needle electrospinning, a number of needles are located in specific fashions in order to increase production rate without allowing interference among needles [108].

Needleless electrospinning systems utilize whole liquid surface rather than needles to increase production output. Multiple jets are ejected from the fiber forming liquid under strong electrical field [109].

In template melt extrusion, nanofibers are produced in the cylindrical holes of an impervious membrane via oxidative polymerization reactions. Nanofibers can be produced from polymers, ceramics, metals, and semiconductors. The length of the nanofibers is determined by the thickness of the membrane, which lies between 5 and 50 mm [110].

Self-assembly is a bottom-up method where molecules are utilized as building blocks to build nanofibers [6, 99].

Drawing process is another interesting means of nanofiber formation. In this technique, a millimetric droplet of a solution is placed on a surface and the solvent is allowed to vaporize. A micropipette is dipped into this droplet close to its periphery and is then withdrawn. During withdrawal from the drop, a nanofiber is pulled out. Each drop can produce several nanofibers by this means [111].

Force spinning is another novel nanofiber production method resembling electrospinning where centrifugal force replaces the electrical field. In this technique, fiber forming material is heated and rotated at a high speed at the nozzle where nanofibers are extruded. Force spinning is advantageous in terms of elimination of strong electrical field, and flexibility in the selection of conducting and nonconducting materials. Furthermore, no disadvantages entailing solvent removal and recovery are present in the force spinning method [112]. More information related to different nanofiber production approaches can be found in Chapter 9 [99].

1.10 Nanotechnology Characterization Methods

As mentioned above, incorporation of nanoscale or nanostructured materials can impart numerous characteristics to textiles including smart functionalities. Nevertheless, utilization of nanomaterials entails some difficulties due to their inherent properties. This necessitates close monitoring of properties such as average particle dimension, dimension range, particle diffusion, presence of elements, and so on [43].

These parameters can be determined by use of various advanced characterization methods including scanning electron microscopy (SEM), transmission electron microscopy (TEM), atomic force microscopy (AFM), X-ray diffraction (XRD), Raman spectroscopy, and X-ray photon spectroscopy (XPS) [43].

Nanotechnological characterization methods can be grouped as imaging methods, spectroscopic techniques, methods using X-rays, size distribution, and zeta potential analyses [113].

For a very long time, optical microscopes have been utilized to observe micron-level materials that cannot be perceived by the human eye in detail. However, at the nanoscale, the optical microscopes are not sufficient based on aberrations and the lower limit of light wavelengths. Here, other imaging techniques come into play such as scanning electron microscopy (SEM), transmission electron microscopy/high-resolution transmission electron microscopy (TEM/HRTEM), scanning tunneling microscopy (STM), atomic force microscopy (AFM), and alike, which can be used to observe sub-micron-sized structures by presenting images with a very high magnification [43].

In AFM, a sharp tip on a cantilever reads the surface topography of a studied material. SEM utilizes a focused electron beam, which strikes and backscatters [114]. Among nanotechnological characterization methods, the transmission electron microscopy technique uses an electron beam that is transmitted through an ultrathin film of the material. The electron beam interacts with the material as it passes through the specimen. The transmitted electrons are used to form an image that is magnified and focused [43]. In STM, by utilization of piezoelectric tube and tunneling current, the surface topographies of materials can be observed at the nanolevel [115].

FTIR (Fourier transform infrared), Raman, and UV–Vis spectrums can be listed as spectroscopy methods. These techniques are very important in characterization of nanoparticles. FTIR spectroscopy detects absorption and/or emission based on asymmetric bonds’ movements; thus, it provides knowledge about the chemical structures. The Raman spectroscopy measures inelastic scattering of monochromatic light interacted with a sample. The changes in the incident and the re-emitted light give information about the chemical and physical structure of the studied material. UV–Vis spectroscopy (ultraviolet–visible spectroscopy) is a method of determining nanoparticle properties based on measuring 180–900 nm light rays [60, 113, 116–118].

Among X-ray methods, EDX (energy dispersive X-ray analysis) technology, which usually accompanies SEM, allows us to determine the composition and concentration of nanoparticles located at the observed material surface, if the material includes heavy metals such as gold palladium and silver nanoparticles [43, 119, 120]. XRD utilizes interaction of X-rays and the sample and gives information about the crystal structure, crystallite size, crystallinity, and phases of the sample [121]. XPS analysis is analogous to SEM imaging, where X-rays take the place of the electron beam [122].

1.11 Challenges and Future Studies

One of the major challenges of smart nanotextiles is implementation of laboratory-scale studies to the mass-production stage as in the case with other emerging technologies. This is especially valid for electrospinning process. Thus, different modifications of the electrospinning method as well as alternative nanomaterial production methods have been developed for optimization of this process to suit large-scale production. It should be noted that not only the production processes but also the characterization procedures should be compatible with the macro-scale applications. On the other hand, some nanomaterials of smart nanotextiles have already found use in commercial applications. These nanomaterials include carbon nanotubes, zinc oxide, titanium dioxide, silicon dioxide, Al₂O₃, and silver [46].

Another major matter related to smart nanotextiles is their impact on the environment and human health. Effects of nanomaterials on the environment and human health are not yet fully known. Thus, extensive investigations should be carried out to detect unwanted effects of this new class of materials, especially those that have close contact with the skin, and more importantly, textiles that are used in vivo. The effects of nanomaterials in the workplace during production and storage stages including those of byproducts and waste water, as well as the effects to the end user during service life and to the environment after disposal, should be closely considered. The effects on the end user relate with the desired/undesired release from the textiles to the human body. Effective bonding/encapsulation of nanomaterials can prevent unwanted release. Potential effects of nanomaterials on health may include DNA damage, passing through and impairing tissue membranes, skin reactions, digestive and respiratory system disorders, and nerve system impairment. To the best of our knowledge, short-term negative effects of nanomaterials on healthy skin have not been reported yet [34]. It should be noted that the most critical negative effect of nanomaterials, as in the case of other materials, is when respired, as it can directly mix with blood, than when digested or when contacted through skin [58].

In order for smart functionalities to take place, energy is, of course, needed. This energy is conventionally provided from an outside source including rechargeable batteries. On the other hand, in advanced examples, smart components are able to harvest and store energy, as in the case of nanogenerators. This revolutionary invention of nanogenerators renders smart textiles more comfortable, versatile, practical, and fashionable. In the future, these nanogenerators can harvest energy even for other devices such as mobile phones [10].

Biomedicine is an important area where there is a great market potential. Smart nanotextiles can be used for the elderly, the sick, and the sports people. IOT (Internet of things) is another future reality, in which the smart nanotextiles can play a role [10].

Major progress occurs when different disciplines meet. Smart nanotextiles are a very significant example of this where areas of textiles, electronics, polymer science, and nanotechnology intersect. We do not expect the textile of the future to be just cotton, viscose, or polyester fabrics. To the contrary, wearables “equipped” with smart functionality will form the future of textiles.

1.12 Conclusion

Textiles present a remarkable series of substrates in order to serve numerous smart functions in an array of fields. Smart functionalities exhibit reversible reactions triggered by an external stimulus, that is, properties of medium, physical, chemical, electrical, etc. Introduction of smart functionalities leads to conversion of textiles into environmental-responsive devices that possess the ability to sense, react to, and adapt to surrounding conditions. By incorporation of smart nanocomponents, it has become possible to obtain advanced properties to cater needs in vast areas of applications including biomedicine, defense, entertainment, and others without compromising the comfort and aesthetics of textiles.

When smart nanotextiles serve their intended duty, this should not be at the expense of textile performance, including flexibility, breathability, comfort, and aesthetics. This can be achieved by use of nanoscale components, which do not form a thick, heavy addition that alters the appearance and drape of clothing. On the other hand, smart nanocomponents should endure the conditions that textiles typically undergo: straining, laundering, and alike. This is where the smart nanocomponent should comply with the rest of the clothing, and a good bonding between the nanomaterial and the textile substrate should be obtained.

Use of smart nanotextiles is not without questions. Use of novel materials necessitates avoidance of adverse effects on human and environmental ecology. This can be attained by assuring successful nanomaterial production, treatment, and bonding procedures, as well as realizing effective nanotechnological characterization methods. Another major challenge is conveying the laboratory-scale successes into the commercial stage. The production rates of nanomaterials are far from catering the mass community needs at the moment. As these problems are going to be solved one by one, we will be seeing that the growing success of smart nanotextiles will exceed our wildest expectations.

References

1. Yilmaz, N. D., Cassill, N. L., and Powell, N. B., Turkish towel’s place in the global market, J. Text. Apparel Tech. Manag., 5, 4, 1–43, 2007.

2. Chika, Y.-B. and Adekunle, S. A., Smart fabrics—wearable technology, Int. J. Eng. Technol. Manag. Res., 4, 10, 78–98, 2017.

3. Mecnika, V., Hoerr, M., Krievins, I., Jockenhoevel, S., and Gries, T., Technical embroidery for smart textiles: Review, Mater. Sci. Text. Cloth. Technol., 9, 56–63, 2014.

4. Syduzzaman, M., Patwary, S. U., Farhana, K., and Ahmed, S., Textile science & engineering smart textiles and nano-technology: A general overview, Text. Sci. Eng., 5, 1, 1–7, 2015.

5. Yang, E. et al., Nanofibrous smart fabrics from twisted yarns of electrospun piezopolymer, ACS Appl. Mater. Interfaces, 9, 28, 24220–24229, 2017.

6. Yilmaz, N. D., Multi-component, semi-interpenetrating-polymer network and interpenetrating-polymer-network hydrogels: Smart materials for biomedical applications abstract, in Functional Biopolymers, Thakur, V. K. and Thakur, M. K. (Eds.) Springer, 2017.

7. Stoppa, M. and Chiolerio, A., Wearable electronics and smart textiles: A critical review, Sensors, 14, 11957–11992, 2014.

8. Song, J., Nanowires for smart textiles, in Smart Textiles: Wearable Nanotechnology, Yılmaz, N. D. (Ed.) Wiley-Scrivener, 2018.

9. Mahltig, B., Nanosols for smart textiles, in Smart Textiles: Wearable Nanotechnology, Yılmaz, N. D. (Ed.) Wiley-Scrivener, 2018.

10. Pu, X., Hu, W., and Wang, Z. L., Nanogenerators for smart textiles, in Smart Textiles: Wearable Nanotechnology, Yılmaz, N. D. (Ed.) Wiley-Scrivener, 2018.

11. Mattila, H., Yarn to Fabric: Intelligent Textiles, in Textiles and Fashion, Sinclair, R. (Ed.) Woodhead Publishing, pp. 355–376, 2015.

12. Ebara, M. et al., Smart Biomaterials. Springer Japan, 2014.

13. Bougia, P., Karvounis, E., and Fotiadis, D. I., Smart medical textiles for monitoring pregnancy, in Smart Textiles for Medicine and Healthcare, Van Langenhove, L. (Ed.) Woodhead Publishing, pp. 183–205, 2007.

14. McCann, J., Smart medical textiles in rehabilitation, in Smart Textiles for Medicine and Healthcare, Van Langenhove, L. (Ed.) Woodhead Publishing, 2007.

15. Qin, Y., Smart wound-care materials, in Smart Textiles for Medicine and Healthcare, Van Langenhove, L. (Ed.) Woodhead Publishing, 2007.

16. Khan, F. and Tanaka, M., Designing smart biomaterials for tissue engineering, Int. J. Mol. Sci., 19, 17, 1–14, 2018.

17. Ortelli, S., Costa, A. L., and Dondi, M., TiO₂ nanosols applied directly on textiles using different purification treatments, Materials (Basel), 8, November, 7988–7996, 2015.

18. Guo, C., Zhou, L., and Lv, J., Effects of expandable graphite and modified ammonium polyphosphate on the flame-retardant and mechanical properties of wood flour-polypropylene composites, Polym. Polym. Compos., 21, 7, 449–456, 2013.

19. Xu, F., Ma, L., Huo, Q., Gan, M., and Tang, J., Microwave absorbing properties and structural design of microwave absorbers based on polyaniline and polyaniline/magnetite nanocomposite, J. Magn. Magn. Mater., 374, 311–316, 2015.

20. Bayat, M., Yang, H., and Ko, F., Electrical and magnetic properties of Fe₃O₄/carbon composite nanofibres, in SAMPE, 2010.

21. “EU project launches €2.4m competition to create ethical and sustainable wearable technologies and smart textiles,” 2017.

22. National Science Foundation, 2018. https://www.nsf.gov/awardsearch/showAward?AWD_ID=1652538.

23. O’Brien, M. and Walton M., These smart threads could save lives, National Science Foundation, 2016. https://www.nsf.gov/news/special_reports/science_nation/biomedtextiles.jsp.

24. Niiyama, E., Fulati, A., and Ebara, M., Responsive polymers for smart textiles, in Smart Textiles: Wearable Nanotechnology, Yılmaz, N. D. (Ed.) Wiley-Scrivener, 2018.

25. Pause, B., Application of phase change and shape memory materials in medical textiles, in Smart Textiles for Medicine and Healthcare, Van Langenhove, L. (Ed.) Woodhead Publishing, 2007.

26. Yilmaz, N. D., Nanocomposites for smart textiles, in Smart Textiles: Wearable Nanotechnology, Yılmaz, N. D. (Ed.) Wiley-Scrivener, 2018.

27. Zysset, C., Cherenack, K., Kinkeldei, T., and Tröster, G., Weaving integrated circuits into textiles, in International Conference on Wearable Computers, 2010.

28. Peterson, J., Carlsson, J., and Bratt, M., Smart textiles for knitted products—prototype factory, in AUTEX 2009 World Textile Conference, 2009.

29. Aibibu, D., Hild, M., and Cherif, C., An overview of braiding structure in medical textile: Fiber-based implants and tissue engineering, in Advances in Braiding Technology: Specialized Techniques and Applications, Kyosev, Y. (Ed.) Woodhead Publishing, 2016.

30. Krucińska, I., Skrzetuska, E., Surma, B., and Gliścińska, E., Technologies involved in the manufacture of smart nonwoven fabrics, in Non-woven Fabrics, Jeon, H.-Y. (Ed.) Intechopen, 2016.

31. Šahta, I., Vališevskis, A., Baltiņa, I., and Ozola, S., Development of textile based sewn switches for smart textile, Adv. Mater. Res., 1117, 235–238, 2015.

32. Gashti, M. P., Alimohammadi, F., Song, G., and Kiumarsi, A., Characterization of nanocomposite coatings on textiles: A brief review on microscopic technology, 1424–1437, 2012.

33. Botticini, F., Make your own smart textile. Experimentation of EdM conductive ink on textiles and development of a specific writing instrument for ink deposition on fabric. Politecnico Milanı, 2016.

34. Gashti, M. P., Pakdel, E., and Alimohammadi, F., Nanotechnology-based coating techniques for smart textiles, in Active Coatings for Smart Textiles, June. Elsevier Ltd, pp. 243–268, 2016.

35. Wilson, A., Ten sensors per fibre with Xelflex, Smart Text. Nanotechnol., 1, 2017.

36. Amft, O. and Habetha, J., Smart medical textiles for monitoring patients with heart conditions, in Smart Textiles for Medicine and Healthcare, Van Langenhove, L. (Ed.) Woodhead Publishing, 2007.

37. Huang, C.-T., Tang, C.-F., and Shen, C.-L., A wearable textile for monitoring respiration, using a yarn-based sensor, in Tenth IEEE International Symposium on Wearable Computers, 2006.

38. Nair, A., Chowdhury, N., and Chowdhury, T., Smart clothes, Int. J. Adv. Res. Eng. Technol., 7, 5, 18–27, 2016.

39. Chen, J. et al., Micro-cable structured textile for simultaneously harvesting solar and mechanical energy, Nat. Energy, 1–8, 2016.

40. Lin, Z. et al., Large-scale and washable smart textiles based on triboelectric nanogenerator arrays for self-powered sleeping monitoring, Adv. Funct. Mater., 28, 1, 1704112, 2017.

41. Pakdel, E., Fang, J., Sun, L., and Wang, X., Nanocoatings for smart textiles, in Smart Textiles: Wearable Nanotechnology, Yılmaz, N. D. (Ed.) Wiley-Scrivener, 2018.

42. Ghosh, D. S., Ultrathin Metal Transparent Electrodes for the Optoelectronics Industry. Springer, 2013.

43. Joshia, M., Bhattacharyya, A., and Ali, S. W., Characterization techniques for nanotechnology applications in textiles, Indian J. Fibre Text. Res., 33, 304–317, 2008.

44. Raab, C., Simkó, M., Fiedeler, U., Nentwich, M., and Gazsó, A., Production of nanoparticles and nanomaterials, Nano Trust Dossiers, 6, July, 1–4, 2017.

45. Zhu, Y., Zhang, J. C., Zhai, J., and Al, E., Multifunctional carbon nanofibers with conductive, magnetic and superhydrophobic properties, Chemphyschem, 7, 336–341, 2006.

46. Wan, L. Y., Nanofibers for smart textiles, in Smart Textiles: Wearable Nanotechnology, Yılmaz, N. D. (Ed.) Wiley-Scrivener, 2018.

47. Yang, M. et al., Single flexible nanofiber to simultaneously realize electricity-magnetism bifunctionality, Mater. Res., 19, 2, 2016.

48. Zhong, J. et al., Fiber-based generator for wearable electronics and mobile medication, ACS Nano, 8, 6273, 2014.

49. Wu, H., Krifa, M., and Koo, J. H., Flame retardant polyamide 6/nanoclay/intumescent nanocomposite fibers through electrospinning, Text. Res. J., 84, 1106–1118, 2014.

50. Periolatto, M., Ferrero, F., Montarsolo, A., and Mossotti, R., Hydrorepellent finishing of cotton fabrics by chemically modified TEOS based nanosol, Cellulose, 20, 1, 355–364, 2013.

51. Yamamoto, M. et al., Theoretical explanation of the Lotus Effect: Superhydrophobic property changes by removal of nanostructures from the surface of a Lotus leaf, Langmuir, 31, 26, 7355–7363, 2015.

52. Zhan, N. et al., A novel multinozzle electrospinning process for preparing superhydrophobic PS films with controllable bead-on-string/microfiber morphology, J. Colloid Interface Sci., 345, 2, 491–495, 2010.

53. Jiang, L., Zhao, Y., and Zhai, J., A lotus-leaf-like superhydrophobic surface: A porous microsphere/nanofiber composite film prepared by electrohydrodynamics, Angew Chem Int., 116, 4438–4441, 2004.

54. Wagner, N. and Theat, P., Light-induced wettability changes on polymer surfaces, Polymer (Guildf), 5, 16, 3436–3453, 2014.

55. Muthiah, P., Boyle, T. J., and Sigmund, W., Thermally induced rapid wettability switching of electrospun blended polystyrene/poly(N-isopropylacrylamide) nanofiber mats, Macromol. Mater. Eng., 298, 12, 2013.

56. Zhu, Y., Feng, L., Xia, F., and Jiang, L., Chemical dual-responsive wettability of superhydrophobic pani-pan coaxial nanofibers, Macromol. Rapid Commun., 28, 10, 1135–1141, 2007.

57. Hanna, E. G. and Tait, P. W., Limitations to thermoregulation and acclimatization challenge human adaptation to global warming, Int. J. Environ. Res. Public Health, 12, 7, 8034–8074, 2015.

58. Yilmaz, N. D., Design of acoustic textiles: Environmental challenges and opportunities for future direction, in Textiles for Acoustic Applications, Nayak, R. and Padhye, R. (Eds.) Springer, 2016.

59. Chalco-Sandoval, W., Fabra, M. J., López-Rubio, A., and Lagaron, J. M., Development of an encapsulated phase change material via emulsion and coaxial electrospinning, J. Appl. Polym. Sci., 133, 36, 43903, 2016.

60. Yilmaz, N. D., Konak, S., Yilmaz, K., Kartal, A. A., and Kayahan, E., Characterization, modification and use of biomass: Okra fibers, Bioinspired, Biomim. Nanobiomaterials, 5, 3, 85–95, 2016.

61. Berendjchi, A., Khajavi, R., and Yazdanshenas, M. E., Application of nanosols in textile industry, Int. J. Green Nanotechnol., 1, 1–7, 2013.

62. Mahltig, B. and Textor, G., Nanosols and Textiles. World Scientific Publishing, 2007.

63. Stegmaier, T., Recent advances in textile manufacturing technology, in The Global Textile and Clothing Industry, Shishoo, R. (Ed.) Woodhead Publishing, 2012.

64. Kopeček, J., Hydrogel biomaterials: A smart future?, Biomaterials, 28, 34, 5185–5192, 2007.

65. Kumar, A., Smart polymeric biomaterials: Where chemistry & biology can merge.

66. Peppas, N. A., Hydrogels, in Biomaterials Science: An Introduction to Materials in Medicine, Ratner, B. D. (Ed.) California: Academic Press, USA, pp. 100–107, 2004.

67. Paleos, G. A., What are hydrogels?, https://www.scribd.com/document/366622248/What-Are-Hydrogels, 2012.

68. Lee, S. C., Kwon, I. K., and Park, K., Hydrogels for delivery of bioactive agents: A historical perspective, Adv. Drug Deliv. Rev., 65, 1, 17–20, 2013.

69. Yilmaz, N. D., Khan, G. M. A., and Yilmaz, K., Biofiber reinforced acrylated epoxidized soybean oil (AESO) composites, in Handbook of Composites from Renewable Materials, Physico-Chemical and Mechanical Characterization, Thakur, V. K. and Thakur, M. K. (Eds.) Wiley-Scrivener, pp. 211–251, 2017.

70. Sandeep, C., Harikumar, S. L., and Kanupriya, Hydrogels: A smart drug delivery system, Int. J. Res. Pharm. Chem., 2, 3, 603–614, 2012.

71. Ranzoni, A. and Cooper, M. A., The growing influence of nanotechnology in our lives, in Micro and Nanotechnology in Vaccine Development, Skwarczynski, M. and Toth, I. (Eds.) Elsevier Inc., pp. 1–10, 2017.

72. Singh, A. K., The past, present, and the future of nanotechnology, in Engineered Nanoparticles Structure, Properties and Mechanisms of Toxicity, Singh, A. K. (Ed.) Elsevier, pp. 515–525, 2016.

73. Clark, D. P. and Pazdernik, N. J., Nanobiotechnology, in Biotechnology, 2nd ed., Clark, D. P. and Pazdernik, N. (Eds.) Elsevier, 2016.

74. Helman, A., Borgström, M. T., van Weert, M., Verheijen, M. A., and Bakkers, E. P. A. M., Synthesis and electronic devices of III–V nanowires, in Encyclopedia of Materials: Science and Technology, 2nd ed., Buschow, K. H. J., Cahn, R. W., Flemings, M. C., Ilschner, B., Kramer, E. J., Mahajan, S., and Veyssière, P. (Eds.) Elsevier Ltd, pp. 1–6, 2008.

75. Tisch, U. and Haick, H., Arrays of nanomaterial-based sensors for breath testing, in Volatile Biomarkers, Amann, A. and Smith, D. (Eds.) Elsevier B V, 2013.

76. Sharma, H. S., Muresanu, D. F., Sharma, A., Patnaik, R., and Lafuente, J. V., Nanoparticles influence pathophysiology of spinal cord injury and repair, in Progress in Brain Research, Howard, C. J. (Ed.) Elsevier, pp. 154–180, 2009.

77. Duan, X., Nanowire thin films for flexible macroelectronics, in Encyclopedia of Materials: Science and Technology, 2nd ed., Buschow, K. H. J., Cahn, R. W., Flemings, M. C., Ilschner, B., Kramer, E. J., Mahajan, S., and Veyssière, P. (Eds.) Elsevier, pp. 1–10, 2010.

78. Hyland, M., Hunter, H., Liu, J., Veety, E., and Vashaee, D., Wearable thermoelectric generators for human body heat harvesting, Appl. Energy, 182, 518–524, 2016.

79. Li, Z., Shen, J., Abdalla, I., Yu, J., and Ding, B., Nanofibrous membrane constructed wearable triboelectric nanogenerator for high performance biomechanical energy harvesting, Nano Energy, 36, 341–348, 2017.

80. Wang, Y., Yang, Y., and Wang, Z. L., Triboelectric nanogenerators as flexible power sources, Npj Flex. Electron., 1, 2017.

81. Fan, F. R., Tian, Z. Q., and Wang, Z. L., Flexible triboelectric generator, Nano Energy, 1, 328–334, 2012.

82. Zhu, G. et al., A shape-adaptive thin-film-based approach for 50% high-efficiency energy generation through micro-grating sliding electrification, Adv. Mater., 26, 23, 3788–3796, 2014.

83. Xie, Y. et al., Grating-structured freestanding triboelectric-layer nanogenerator for harvesting mechanical energy at 85% total conversion efficiency, Adv. Mater., 26, 38, 6599–6607, 2014.

84. Camargo, P. H. C., Satyanarayana, K. G., and Wypych, F., Nanocomposites: Synthesis, structure, properties and new application opportunities, Mater. Res., 12, 1, 1–39, 2009.

85. Nguyen-Tri, P., Nguyen, T. A., Carriere, P., and Xuan, C. N., Nanocomposite coatings: Preparation, characterization, properties, and applications, Int. J. Corros., 2018, 1–19, 2018.

86. Hári, J. and Pukánszky, B., Nanocomposites: Preparation, structure, and properties, in Applied Plastics Engineering Handbook, Kutz, M. (Ed.) William Andrew, pp. 109–142, 2011.

87. Lateef, A. and Nazir, R., Metal nanocomposites: Synthesis, characterization and their applications, in Science and Applications of Tailored Nanostructures, Di Sia, P. (Ed.) One Central Press, pp. 239–256, 2018.

88. Bratovčić, A., Odobašić, A., Ćatić, S., and Šestan, I., Application of polymer nanocomposite materials in food packaging, Croat. J. Food Sci. Technol., 7, 2, 86–94, 2015.

89. Edwards, J. V., Prevost, N., French, A., Concha, M., DeLucca, A., and Wu, Q., Nanocellulose-based biosensors: Design, preparation, and activity of peptide-linked cotton cellulose nanocrystals having fluorimetric and colorimetric elastase detection sensitivity, Engineering, 5, 20–28, 2013.

90. Chowdhury, S., Olima, M., Liu, Y., Saha, M., Bergman, J., and Robison, T., Poly dimethylsiloxane/carbon nanofiber nanocomposites: Fabrication and characterization of electrical and thermal properties, Int. J. Smart Nanomater., 7, 4, 236–247, 2016.

91. Yilmaz, N. D., Koyundereli Cilgi, G., and Yilmaz, K., Natural polysaccharides as pharmaceutical excipients, in Handbook of Polymers for Pharmaceutical Technologies, Volume 3, Biodegradable Polymers, Thakur, V. K. and Thakur, M. K. (Eds.) Wiley-Scrivener, pp. 483–516, 2015.

92. Lv, P. et al., A highly flexible self-powered biosensor for glucose detection by epitaxial deposition of gold nanoparticles on conductive bacterial cellulose, Chem. Eng. J., 351, 177–188, 2018.

93. Abdi, M. M., Abdullah, L. C., Tahir, P. M., and Zaini, L. H., Cellulosic nanomaterials for sensing applications, in Handbook of Green Materials 3 Self- and Direct Assembling of Bionanomaterials, Oksman, K., Mathew, A. P., Bismarck, A., Rojas, O., and Sain, M. (Eds.) World Scientific Publishing, pp. 197–212, 2014.

94. Yilmaz, N. D., Biomedical applications of microbial cellulose nanocomposites, in Biodegradable Polymeric Nanocomposites: Advances in Biomedical Applications, Wiley-Scrivener, pp. 231–249, 2015.

95. Kim, J.-H. et al., Review of nanocellulose for sustainable future materials, Int. J. Precis. Eng. Manuf. Technol., 2, 2, 197–213, 2015.

96. Kim, J. and Seo, Y. B., Electro-active paper actuators, Smart Mater. Struct., 11, 355–360, 2002.

97. Grancaric, A. M. et al., Conductive polymers for smart textile applications, J. Ind. Text., 48, 3, 612–642, 2017.

98. Kurahatti, R. V., Surendranathan, A. O., Kori, S., Singh, N., Kumar, A. V. R., and Srivastava, S., Defence applications of polymer nanocomposites, Def. Sci. J., 60, 5, 551–563, 2010.

99. Nayak, R., Production methods of nanofibers for smart textiles, in Smart Textiles: Wearable Nanotechnology, Yılmaz, N. D. (Ed.) Wiley-Scrivener, 2018.

100. Nayak, R., Padhye, R., Kyratzis, I. L., Truong, Y. B., and Arnold, L., Recent advances in nanofibre fabrication techniques, Text. Res. J., 82, 2, 129–147, 2011.

101. Li, Z. and Wang, C., One-Dimensional Nanostructures. Berlin, Heidelberg, Springer-Verlag, 2013.

102. Shi, J., Guobao, W., Chen, H., Zhong, W., Qiu, X., and Xing, M. M. Q., Schiff based injectable hydrogel for in situ pH-triggered delivery of doxorubicin for breast tumor treatment, Polym. Chem., 5, 6180–6189, 2014.

103. Li, J. et al., Filtration of fine particles in atmospheric aerosol with electrospinning nanofibers and its size distribution, Sci. China Technol. Sci., 231, 7, 597–616, 2017.

104. Chen, S., Ye, W., and Hou, H., Electrospun fibrous membranes as separators of lithium-ion batteries, in Electrospun Nanofibers for Energy and Environmental Applications. Nanostructure Science and Technology, Ding, B., and Yu, J. (Eds.) Berlin, Heidelberg, Springer, 2014.

105. Ngadiman, N. H. A., Noordin, M. Y., Idris, A., and Kurniawan, D., A review of evolution of electrospun tissue engineering scaffold: From two dimensions to three dimensions, Proc. Inst. Mech. Eng. Part H J. Eng. Med., 231, 7, 597–616, 2017.

106. Liu, M., Duan, X.-P., Li, Y.-M., Yang, D.-P., and Long, Y.-Z., Electrospun nanofibers for wound healing, Mater. Sci. Eng. C, 76, 1413–1423, 2017.

107. Weng, L. and Xie, J., Smart electrospun nanofibers for controlled drug release: Recent advances and new perspectives, Curr. Pharm. Des., 21, 15, 1944–1959, 2015.

108. Tian, L., Zhao, C., Li, J., and Pan, Z., Multi-needle, electrospun, nanofiber filaments: Effects of the needle arrangement on the nanofiber alignment degree and electrostatic field distribution, Text. Res. J., 85, 6, 621–631, 2015.

109. Yu, M. et al., Recent advances in needleless electrospinning of ultrathin fibers: From academia to industrial production, Macromol. Mater. Eng., 302, 7, 1700002, 2017.

110. Li, H., Ke, Y., and Hu, Y., Polymer nanofibers prepared by template melt extrusion, J. Appl. Polym. Sci., 99, 3, 1018–1023, 2006.

111. Xing, X., Wang, Y., and Li, B., Nanofiber drawing and nanodevice assembly in poly(trimethylene terephthalate), Opt. Express, 16, 14, 2018.

112. Hammami, M. A., Krifa, M., and Harzallah, O., Centrifugal force spinning of PA6 nanofibers—processability and morphology of solution-spun fibers, J. Text. Inst., 105, 6, 637–647, 2014.

113. Pillai, M. M., Senthilkumar, R., Selvakumar, R., and Bhattacharyya, A., Characterization methods of nanotechnology based smart textiles, in Smart Textiles: Wearable Nanotechnology, N. D. Yılmaz, (Ed.) Wiley-Scrivener, 2018.

114. Smith, B., The differences between atomic force microscopy and scanning electron microscopy, Azo Mater., 2015.

115. Schmid, M., The scanning tunneling microscope, Technical University of Wien, 2011. https://www.iap.tuwien.ac.at/www/surface/stm_gallery/stm_schematic.

116. Wu, J.-B., Lin, M.-L., Cong, X., Liua, H.-N., and Tan, P.-H., Raman spectroscopy of graphene-based materials and its applications in related devices, Chem. Soc. Rev., 47, 5, 1822–1873, 2018.

117. Ultraviolet–visible spectrometer, Royal Society of Chemistry, 2018. http://www.rsc.org/publishing/journals/prospect/ontology.asp?id=CMO:0001803&MSID=B821416F.

118. Raman spectroscopy basics, Princeton Instruments. http://web.pdx.edu/~larosaa/Applied_Optics_464-564/Projects_Optics/Raman_Spectrocopy/Raman_Spectroscopy_Basics_PRINCETON-INSTRUMENTS.pdf.

119. Piazza, G. J., Nuñez, A., and Foglia, T. A., Epoxidation of fatty acids, fatty methyl esters, and alkenes by immobilized oat seed peroxygenase, J. Mol. Catal. B Enzym., 21, 3, 143–151, 2003.

120. Fay, F., Linossier, I., Langlois, V., Haras, D., and Vallee-Rehel, K., SEM and EDX analysis: Two powerful techniques for the study of antifouling paints, Prog. Org. Coatings, 54, 3, 216–223, 2005.

121. The X-ray diffraction small research facility: What is XRD?, The University of Sheffield, 2018. https://www.sheffield.ac.uk/materials/centresandfacilities/x-ray-diffraction/whatxrd.

122. XPS/ESCA, Physical Electronics, 2018. https://www.phi.com/surface-analysis-techniques/xps-esca.html.