Abstract
The textile industry is rapidly shifting toward sustainability due to increasing environmental concerns, regulatory pressures, and consumer demand for eco-friendly products. The global functional textile market reached approximately USD 4.72 billion by 2020, with a compound annual growth rate of 30-3.58%. However, conventional functional finishing relies on over 8,000 chemicals, including formaldehyde-based resins, per fluorinated compounds (PFCs), and heavy metals, many of which pose serious environmental and health risks. This review, based on the analysis of 172 references, presents a comprehensive overview of sustainable materials and methods for textile functionalization. It highlights bio-based, animal-derived, hybrid, and green-synthesized nanomaterials that range from 1-100nm, used to impart functional properties such as antimicrobial activity, UV protection, self-cleaning, and flame retardancy. Sustainable application techniques, including coating, sol-gel processing, layer-by-layer assembly, encapsulation, and enzymatic treatments, are critically discussed. Further, key challenges related to durability, scalability, material compatibility, and regulatory compliance are examined. Emerging trends, including multifunctional bio-nanocomposites, circular textile systems, and digitalized green manufacturing, are also explored. This review provides a concise roadmap for developing high-performance, sustainable functional textiles with reduced environmental and health impacts.
Keywords
1. Introduction
Functional finishing of textile materials refers to the process of treating fabrics to provide them with additional properties beyond their basic structural and aesthetic characteristics. 1 There is a growing demand for functional products that offer comfort and meet specific needs. These needs can be addressed using newly developed technologies in the industrial sector. 2 With the advancement of numerous technologies in antiquity, the functionalization of various surfaces has been of interest. To change the visual appeal, functional potential, and environmental protection, such as resistance against oxidants, many surface coatings and painting materials and processes have been developed. 3 Currently, the functional textiles market is growing with an excellent growth rate of 33.58% between 2015 to 2020. The global functional textile market reached 4.72 billion US$ by 2020. India is a prime manufacturer of apparel and textiles and the fourth-largest exporter in the international sector. The functional textile sector has encountered a compound annual growth rate (CAGR) of 30% from 2015 to 2020 due to strong automotive, fitness, fashion, healthcare, military, and sports textiles. 4 Despite the growing demand for functional textiles, the traditional finishing material and methods result in environmental hazards. This leads to property raising significant safety concerns, particularly in environments where the hazardous chemicals are directly exposed to the environment. 5 For example, traditional finishing agents such as formaldehyde-based resins, chlorinated flame retardants, per fluorinated compounds (PFCs/PFAS), heavy metal salts, quaternary ammonium compounds, chlorine-based bleaching agents, and alkylphenol ethoxylates have been used. 6 Further, traditionally, finishing methods such as padding, exhaustion, curing, calendaring, heat-setting, mercerization, etc., have been employed. 7 Therefore, sustainable functionalizing material with modern application methods is a crucial area of scientific research with practical implications. 8
Historically, synthetic and natural materials that have been used for functionalization of textiles, such as triclosan, quaternary ammonium, polybiguanides, N-halamines, platinum, and chitosan, which are synthetic and natural substances used for imparting functional properties like antimicrobial activity and UV-protection. 9 However, the rise of fast fashion, characterized by rapid design-to-market cycles and high production volumes, has intensified the reliance on hazardous chemicals even today. More than 8,000 chemicals, such as formaldehyde and its derivatives, are used in production, leaving toxins like glyphosate in cotton, VOCs in printed clothing, and per fluorinated compounds (PFCs) in children’s wear, known for disrupting hormones and posing cancer risks. 10 For example, halogen-containing compounds are the most effective flame retardants for cotton fabrics. However, these substances release cancer-causing dioxins and harmful fumes during combustion, thereby endangering human health and polluting the environment. Consequently, several nations have banned the use of halogen-based flame-retardants. 11 Therefore, the pursuit of sustainable functionalizing methods and materials for the textile industry aims to enhance functionality while minimizing environmental harm. In recent years, various natural materials, such as biomass-based, protein-based, and inorganic materials, along with suitable green functionalization techniques, have been explored as promising sources for developing safer, healthier, and high-performance textile finishes. 12 Nevertheless, because of variations in material characteristics, processing limitations, and performance requirements, the efficient use of sustainable materials and the choice of suitable application methods continue to be major challenges. This review critically examines sustainable functionalization materials and associated application techniques with a focus on reducing hazards to human health and the environment. 13
Moreover, the rising demand for functional textiles aligns with advancements in living standards and technological progress, and there is a significant need for fabrics that are finished in sustainable materials without affecting human health and no environmental hazards. 14 This demand has led to increased interest in sustainable functional agents and treatment methods for developing innovative fabrics with better functional properties. The functionalization of textiles can be categorized into traditional and modern methods. 15 The conventional methods offer the required properties but frequently lack durability and environmental compatibility. 16 Conversely, modern techniques utilize cutting-edge technologies that offer greater durability, multifunctionality, and a reduced environmental impact. 17 Technologies such as sol-gel coatings, 18 layer-by-layer nano-assembly, 19 in-situ nanoparticle synthesis, 20 micro and nanoencapsulation, 21 bio-enzymatic functionalization, 22 eco-friendly green chemistry, 23 and nano-enabled dip/spray coatings. 24 Despite this, identifying the required method that uses sustainable materials and minimizes environmental impact remains a significant challenge in the field of functional finishing of textile research. 25 A wide range of review articles have been published on eco-friendly finishing approaches, both traditional and modern methods, with sustainable as well as traditional finishing materials for functional finishing. 26 These reviews addressed various aspects of material and application methods, including traditional chemicals, sustainable alternatives such as nanomaterials, 27 plant extracts, 28 biomacromolecules, 29 chitosan, and collagen, 30 along with finishing methods (modern and traditional).
However, a comprehensive review on sustainable functionalizing materials and their application methods has not been systematically compiled, as the pursuit of these materials and methods for textile functionalization has emerged as a dynamic and essential area of research. Further, the purpose of this research is to evaluate contemporary functionalization techniques and sustainable materials that potentially take the place of traditional hazardous finishing agents in the textile industry. Additionally, this review is to thoroughly investigate eco-friendly application methods and sustainable materials used in textile functional finishing. In addition to contemporary green application methods that improve performance while minimizing negative effects on the environment and human health, it aims to assess the potential of bio-based, biodegradable, and environmentally benign functionalizing agents. The review also aims to identify current opportunities and restrictions in order to guide the development and adoption of safer, more sustainable functional finishing techniques. These sustainable approaches not only support cleaner production but also align with circular economy principles, promoting renewable resource use, waste reduction, and improved end-of-life outcomes for textile products. In pursuit of this goal, this research is an essential tool. By emphasizing the significance of using the proper sustainable materials and procedures in the functional finishing of textiles, this study distinguishes itself from previous reviews.
2. Overview of textile functionalizing materials and methods
Textiles are traditionally used to conceal human skin, but with scientific management, clothing can be made to fulfil the purposes of various human skin types. Acknowledging the chemical and dermatological complexity of human skin, functional clothing can be used to design the effects of humidity, microorganisms, pH, temperature, and wind. Functional textiles are the newest type of textile material that has been introduced in this regard. 31 In addition to their basic purpose of covering the human body, many garment materials have the capacity to perform additional functions. 32 Functional textiles contribute to the advancement of the conventional technical textiles segment, representing a sector where traditional clothing crosses the usual frontiers and connects with the spheres of biotechnology, cosmetic science, computing potentials, flexible electronics, medicine, and nanotechnology, among others, to achieve the multidimensional and complex demands of the customer. 33
Textile functionalizing materials can be sourced from either from natural or synthetics. The natural one includes the use of polymers, nanoparticles, bio-based agents, microcapsules these are eco-friendly materials. In contrast, synthetic materials such as fluorocarbon polymers, polyurethane (PU), quaternary ammonium compounds (QACs), and formaldehyde-based resins (e.g., DMDHEU) are used to impart functional properties, but they are typically not environmentally friendly. These materials often contain reactive compounds that can effectively bond with the textile surface, imparting desired functional properties while minimizing environmental impact.34,35 Some of the varied functionalization methods used are dip coating, padding, plasma treatment, sol-gel processing, in-situ synthesis, microencapsulation, layer-by-layer deposition, and enzymatic alterations. 36 The desired usefulness, material type, environmental factors, and required level of durability all affect the process selection. With increasing global emphasis on sustainability, the area is moving toward green chemistry techniques, bio-derived materials, waterless technologies, and energy-efficient finishing processes. 37 In general, it is anticipated that the next generation of functional textiles will be defined by the integration of sustainable practices, nanotechnology, and smart materials as innovation accelerates.
3. Need for Sustainability
The use of traditional functionalizing materials and methods is insufficient as society evolves and our needs for creative solutions expand. The fundamental characteristics of conventional textile materials also frequently fail to meet these new challenges. 38 Traditional finishes rely heavily on materials such as fatty acids, silicones, cationic and anionic softeners in softener finishing, 39 fluorocarbons as water-repellent agents, 40 and heavy metal antimicrobial agents. 41 Conventional flame-retardant salts such as ammonium phosphate and ammonium chloride were used because of their effectiveness in flame retardance; however, these chemicals result in an environmental impact. 42 The conventional finish application methods, such as pad-dry-cure and exhaustion, are common application techniques, consume a lot of water and energy. For example, padding can result in 70%-100% wet pickup, needing significant energy for water evaporation during the drying process, which leads to an uneven finish due to active agents’ diffusion. Another common technique of applying the finish is exhaustion or impregnation, which also requires water as a medium and further drying. 43 These old technologies are environmentally costly, generating enormous amounts of wastewater and requiring large amounts of energy, making them inappropriate for the textile industry’s growing commitment to environmental responsibility and its desire for new, high-performance textiles.
This leads the textile industry, with a strong commitment to sustainability, is constantly looking for new and creative ways to manufacture textiles with the pursuit of modern materials and methods that prioritize sustainability, efficiency, and advanced functionality.
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The adoption of new materials such as biomass-based agents, green-synthesized metal nanoparticles (AgNPs, CuO NPs and ZnO NPs etc...) and smart polymers offers a way to achieve durable, high-performance properties along with advanced functional properties, such as self-cleaning, fire retardancy, antimicrobial and UV-protection, while exploring more inherently sustainable options.
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The endeavor of these low-impact, high-efficiency technologies, including in-situ nanoparticle synthesis, layer-by-layer assembly, atomic layer deposition, and molecular layer deposition, is vital for creating next-generation textiles that meet increasing social expectations without harming the environment shown in Figure.
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(Figure 1). Schematic diagram of the key aspect of next-generation textiles
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4. Current Trends in Sustainable Textile Functionalization
4.1. Transition Towards Bio-Based Functional Agents
Textile processing typically involves energy-intensive, water-intensive, chemical-intensive, and environmentally polluting processes. Several chemical finishes are applied to fabrics to improve their durability, comfort, appearance, and functionality. When it comes to high-performance functional textiles for a range of industrial applications, the usage of such treatments is even more prevalent. For example, biocidal nanoparticles are frequently applied to antimicrobial treatments used in medical textile applications. These finishing compounds prevent the biodegradation process from occurring. Consequently, there is a constant rise in the demand for the development of sustainable functionalizing materials utilized in the textile sector Daget. T et al.. 48 In response to growing environmental concerns and increasing regulatory frameworks, the textile industry is actively exploring more sustainable alternatives. Among promising solutions, the integration of biotechnology by leveraging enzymes, biopolymers, plant-and agro-waste-based materials, and microbial metabolites, offers eco-friendlier substitutes for conventional chemical treatments. For example, the surface of PP fabric was activated using oxygen and nitrogen plasma radiation. The plasma-irradiated PP fabric was post-treated with two renewable eco-friendly proteinic biopolymers, namely gelatin and sericin, in the presence and absence of a crosslinking agent. The findings of this study demonstrated that plasma/biopolymer-finished fabrics had improved comfort, including enhanced antistatic properties, better wettability, and increased ultraviolet protection. 49 Therefore, bio-based materials with innovative methods not only can reduce the environmental impact of textile processing but also contribute to improved process efficiency and lower water and energy consumption.
4.2. Transition Toward Sustainable and High-Efficiency Application Methods
The transition toward sustainable and high-efficiency application methods implies a change from conventional, resource-intensive finishing methods characterized by high water and energy consumption, hazardous chemicals, and large waste toward eco-friendly, resource-efficient finishing methods. This movement accentuates functional finishing, where textiles receive extra features such as antibacterial activity, water repellency, UV protection, softness, and durability, but in a sustainable and high-performance way. 50 The aim is to simultaneously reduce environmental impact while increasing finishing efficacy. The sustainable and high-efficiency application methods, including plasma that represent a green way for altering the outer atomic layer without affecting the material’s bulk qualities. Sono processes are explored as methods to improve conventional dyeing and finishing procedures. Layer‐by‐Layer (LbL) self‐assembly is regarded as a green and low‐cost technology that can be employed in wet‐finishing procedures to reduce chemicals, water, and energy consumption while increasing fabric functionality. 50 Shen, Y., et al. 51 studied bio-based flame retardant superhydrophobic coatings by phytic acid/polyethyleneimine Layer-by-Layer assembly on nylon/cotton blend fabrics. The treated fabric showed excellent flame retardant and self-extinguishing behavior, with no after flame or afterglow during vertical burning and a char length of only 35 mm. Thermogravimetric analysis revealed a residual char rate of 43.9%, far exceeding that of untreated fabric (8.6%). Further, the sol-gel method has become a fast-expanding area of research in the field of materials science due to its simple methodology, cost-effectiveness, and environmental friendliness. Thus, it does not require complicated technological installation, which is a plus point for small and medium-sized industries. 52 Therefore, the adoption of these sustainable and high-efficiency application methods not only minimizes environmental impact but also enhances the functional performance of the textile.
5. Categories of Sustainable Functionalizing Materials
As the world shifts towards more sustainable manufacturing, the textile sector is facing mounting pressure to adopt environmentally sustainable practices. One key aspect of this transition is the use of sustainable functionalizing materials, which can be classified based on their origin.
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Sources of sustainable functionalizing materials include plants, animals, minerals, and hybrid sustainable materials.
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With the advancement in material research, new research areas like geo-materials, fire-retardant materials, aromatic materials, nano-textile materials, medical textiles and insect-resistant materials are becoming popular. Numerous licenses have been accounted for various regions of textile finishing, as across the world, researchers are committed to leveraging these interesting areas of material research using sustainable strategies.
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The key strategies that could be adopted to achieve textile sustainability are shown in Figure 2. Different strategies to achieve sustainability in the functional finishing of textiles
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5.1. Plant-Based Functionalizing Materials
5.1.1. Plant Extracts
Plant extracts are bioactive substances obtained from leaves, roots, bark, and flower seeds. 57 Many plant leaves, like tea leaves, and their extracts contain potent metabolic compounds that are used extensively in medicine to treat a wide range of illnesses.
Polyphenolic compounds such as flavonoids, gallic acid, rutin, kaempherol, catechin, quercetin, and phenolic acid are plentiful in their leaves.
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These compounds are used in the functionalization of textiles. For example, natural plant extracts, particularly eucalyptus and hop, were incorporated into knitted fabrics to develop antimicrobial textiles. The antibacterial activity of the functionalized fabrics was evaluated against two pathogenic bacteria (Staphylococcus aureus and Escherichia coli) and one common skin commensal (Staphylococcus epidermidis). Biocompatibility with human skin cells was assessed through MTT assays, TO/PI, and Calcein/PI staining. The results of the study demonstrated that a strong antimicrobial activity of the functionalized textiles against S. aureus and S. epidermidis, with less evident effects on E. coli.
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Ivanovic, V. et al
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studied viscose fabrics treated with plant extracts showed strong functionality. Pomegranate peel and hemp extracts exhibited the highest antibacterial activity against gram-positive bacteria, with a value of 20 mm. Pomegranate peel was most effective against gram-negative bacteria with a value of 17.5 mm. Antioxidant activity was highest for lady’s mantle 80%, mountain germander 76%, and pomegranate peel 70%. Furthermore, natural dyes extracted from mango leaves and mango peel, find sustainable ways of cotton dyeing. Natural coloring agents were extracted using an aqueous extraction technique, and the cotton fabric was dyed using the extracts, followed by mordanting using different mordant types. The dyeing performance of extracted coloring agents was assessed in terms of color values, dye absorption (%), color fastness properties and color strength. The dye extract exhibited a deeper shade, as shown in Figure 3. Natural dyeing of cotton fabric with extracts from mango tree
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The Impact of Selected Plant Extracts and Natural Products of Plant Origin on Skin Regeneration and Wound Healing 63
5.1.2. Essential Oils
In response to growing consumer demand for sustainable and multifunctional fabrics, the textile industry has shifted towards natural and biodegradable finishing agents. Essential oils (EOs) extracted from plants possess innate antimicrobial, insect-repellent, antioxidant and aromatic properties.
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These properties make them attractive alternatives to synthetic chemicals for textile applications. They are widely known to possess various beneficial properties which are vital in numerous fields such as fragrance, flavor and medicine. In light of the increasing emphasis on eco-friendly processes, the application of essential oils presents a viable alternative to synthetic drugs.
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These oils impart functional properties to textiles. For example, Johan, N.A.A., et al
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developed multifunctional textiles by incorporating microencapsulated lemongrass essential oil (LEO) onto cotton-polyester blended fabrics. The functionalization of fabrics using microencapsulated essential oils offers an appealing route to combine textile comfort with bioactive properties. The application of essential oils is limited by their volatility and susceptibility to chemical instability against external stimuli such as light, heat, and moisture. This results in the loss of their therapeutic efficacies and functional properties.
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Nanoencapsulation presents an innovative way to overcome the limitations in utilizing the therapeutic efficacies of EOs for functional textile applications, as shown in Figure 4. Nanoencapsulation strategies for loading essential oils (EOs) in polymeric nanoparticles, showcasing the formation of oil-in-water (O/W) formulations, followed by their impregnation into multifunctional textile finishing
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Key Components of Different Aromatic Plants’ Essential Oils
5.1.3. Natural Dyes
Natural dyes have been used for dyeing fabric, leather, body, hair, for cosmetic purposes, crafts, food coloring, dye-sensitive solar cells, and functional textile finishing.
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They have several advantages over synthetic dyes. Natural colorants are eco-friendly, biocompatible, nonallergenic, and nontoxic. These colorants can be classified according to their chemical structure, such as indigoid, anthraquinone, flavonoid, carotenoid, pyridine, tannin, and quinoid. The unique chemical formations of natural colorants are responsible for their inherent functional properties. Most natural dyes and pigments have UV-resistant properties. Besides, some natural dyes can repel moths and insect.
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Zhang, W., et al
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utilized a Portulaca oleracea L. plant as a natural colorant for wool fabric dyeing with a high color yield at optimum extraction and dyeing conditions. The dyed wool fabrics confirm that superior color depth (K/S value 23.53), biological function as anti-ultraviolet (UPF value 253.47), and anti-bacterial activity (antibacterial rate of Staphylococcus aureus/Escherichia coli was 71.3%/37%). Further, a novel ultrasound-assisted extraction of Rosa canina, utilizing both dry and fresh fruits, explores the potential application of Rosa canina extraction as a natural dye and functional agent for cotton fabrics.
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Natural dyes have attracted more and more attention because of their coloring, functionalization effects, and environmental benefits. Furthermore, dyes extracted from lac and used for coloring and functionalization in silk fabrics. The results show that the dyed silk fabrics have good UV protection, antioxidation, and antibacterial properties, as shown in Figure 5. Schematic presentation of lac pigment extraction and dyeing process
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Studies of Finishing Cotton Fabrics With Natural Dyes 76
5.1.4. Plant-Based Biopolymers
The textile industry is shifting from synthetic polymers to eco-friendly biopolymers, which offer biodegradability and sustainability, reducing environmental impact. Biopolymers are among the most significant materials that researchers have discovered and developed for a wide range of applications. They are necessary to modern life and are used everywhere.
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Some of the biopolymer-based groups include cellulose, starch, pectin, proteins, gums, lignin and tannins.
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The widespread adoption of biopolymers across industries marks a pivotal moment in the quest for sustainable solutions to contemporary challenges.
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Plant-based biopolymers imparting functional properties to textiles, such as UV resistance, flame-retardant, and antimicrobials.
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For example, a sustainable functionalization was achieved for cotton fabrics using screen-printing process and the gallotannin. The results show excellent antibacterial activity, deodorizing property, and ultraviolet-blocking property.
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Further
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Ibrahim, N.A., et al have shown that gelatin-based thickened fabrics were tested for antibacterial activity against Escherichia coli, Staphylococcus aureus, and Candida albicans. Biopolymers such as cyclodextrin are used in textiles for the development of bio-functional fabrics as an alternative to the development of eco-friendly textiles. Figure 6 shows that β-cyclodextrin-modified cotton fabric for medical and hospital applications with photodynamic antibacterial activity using methylene blue. Application of a photodynamic dye on a textile substrate for the production of antimicrobial material for healthcare
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Biopolymers Production From Various Agro-Industrial Waste Substrates 86
5.1.5. Key Challenges and Strengths of Plant-Based Functionalizing Materials
Recent Studies on Natural Finishes in Textile 89
In order to improve the wash fastness of textiles, different attempts have been made. For example, Venkatraman et al. 90 studied that the organic cotton fabrics finished with herbal nano-emulsions via continuous and batch methods retained antimicrobial, antifungal properties and wash fastness after 20 cycles. Therefore, micro- or nano-encapsulation, which safeguards bioactive ingredients and permits controlled release, can enhance the poor fastness of plant-based textile finishes. Layer-by-layer coatings, eco-friendly crosslinkers, and surface pre-treatments such as plasma or ozone improve adhesion and durability, ensuring longer-lasting antibacterial, UV, and fragrance protection without sacrificing fabric quality.
5.2 Animal and Microbial-Based Functionalizing Material
Animal- and microbial-based textile functionalizing materials are derived from sources such as Chitosan, silk, feathers, keratin, microbial pigments, and bacterial cellulose.
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Extracts from chitosan, alginate and collagen hydrolysate are used in the functionalization of textiles. Chitosan is an eco-friendly polymer obtained from the diacylation of chitin and is widely used in the textile industry in finishing processes, and used as an antimicrobial. Alginate, found in brown seaweed as a bioactive compound, is used in the textile industry for medicinal products. On the other hand, collagen hydrolysate is a fiber found in bones and tissues. It has antibacterial properties, which make it suitable to be used in medical textiles for coating fabrics, wound dressings, and implantable medical devices.
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For example, casein found in milk as colloidal casein micelles has amino acids, carbohydrates, and the essential minerals calcium and phosphorus. Which is widely employed in the textile sector for several applications such as printing, Finishing, Sizing, adhesive, dyeing.
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Figure 7 shows multifunctional cotton fabrics coated with novel antibacterial chitosan nano capsules and polyacrylate, demonstrating enhanced protective and functional properties. Schematic representation of cotton fabrics coated with novel antibacterial chitosan nano-capsules and polyacrylate
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Microbial-based functionalizing materials for textiles are obtained from different origins, as shown in Figure 8.
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These materials are used to impart functional properties, as animal and plant-based materials do. For example, Gayathri, V., et al
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studied that bacterial cellulose (BC) obtained from fermentation on a lab scale using a cellulose-producing bacterium called Gluconacetobacter kombuchae (MTCC 69 13) under Hestrin-Schramm (HS) medium, or kombucha-derived bacterial cellulose (KBC) obtained from kombucha available in the market or cotton-cellulose (CC) were chosen for the surface functionalization to find the methodology’s diversity. Finally, contact angle analysis of the surfaces showed the hydrophobic natures of some functionalized BC-based materials, which are important for the practical use of biomaterials in wet climatic conditions. Shows different microbial-based biopolymers used in the functional finishing of textiles. Microbial biopolymers for functional textile applications
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Key Animal- and Microbial-Based Materials Used for Textile Functionalization
5.3. Inorganic and Mineral Functionalizing Materials
Inorganic and mineral textile functionalizing materials are non-organic materials added to textiles to give them extra functions beyond basic fabric performance. 110 Natural inorganic functionalizing materials for textiles are mostly used for imparting flame retardancy. 111 These include a range of substances such as nanoparticles, silica and silicate-based materials, intumescent compounds, ammonium polyphosphate and boron chemicals like borax and boric acid improve the production of protective char layers when used in combined with organic functionalizing materials. 112 For example, aluminum hydroxide and magnesium hydroxide work by releasing water at high temperatures, cooling the fabric, and diluting dangerous gases. 113 Work has been carried out by applying silica nano sol cum water repellent functional finishing on a bleached jute fabric by the pad-dry-cure method. The results revealed that silica nanocomposite finished jute fabric has attained the desirable hydrophobic functionality with 138.6° water contact angle, 17° sliding angle and 10.3° water contact angle hysteresis with semi-durable washing durability. 114
Figure 9 shows the flame retardancy of cotton and polyester-cotton fabrics treated with different concentrations of silica and zinc nanoparticles through a sol-gel finishing technique. Schematics of SiO2 and ZnO nanoparticles functionalized fabric
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Furthermore, inorganic materials, including carbon nanotube, graphene, metal-coated fibers such as nickel, copper, and silver, and metal oxides like indium tin oxide, offer dependable electrical conductivity. These are particularly used in smart and technical textiles that make extensive use of conductive inorganic elements. 116 On the other hand, naturally occurring or processed minerals are widely used to functionalize textiles because of their stability, availability, and multifunctional properties. 117 Clay minerals like montmorillonite and kaolin, zeolites, silica (SiO2), and basalt minerals are widely used in textiles to enhance durability, flame resistance, water repellency, heat resistance, and mechanical strength. 118 For example, a study was done on polymer coatings of textiles using basalt fibers. As the textile substrate, a cotton fabric was used. The results show that optical spectra are recorded in a spectral range from 220 to 1400 nm. By these optical measurements, it is demonstrated that the optical properties for UV-light, visible light and near infrared light are influenced by the basalt-containing coatings. The transmission of UV light is drastically reduced. 119
5.4. Green-Synthesized Metal Nanoparticles
Nanoparticles, measuring 1-100 nm in at least one dimension, can be incorporated into textiles to impart functional properties and improve the mechanical strength of treated textiles.
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Green synthesis of nanoparticles using plant materials, enzymes, animal waste, biopolymers and microorganisms has evolved as a sustainable alternative to conventional techniques that rely on toxic chemicals.
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The natural sources for green synthesis of nanoparticles are shown in Figure 10. Recently, green-synthesized eco-friendly NPs have attracted interest for their potential use in various biological applications. Several studies have demonstrated that green-synthesized NPs are beneficial in multiple medicinal applications for textiles, including anti-cancer treatment, targeted drug delivery, antibacterial properties, antifungal properties, UV-protection and wound healing.
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For example, cotton fabric was functionalized with green synthesized copper oxide nanoparticles and phenolic compounds of Azolla Nilotica algae extracts to impart antibacterial and UV-protection properties. The optimum values obtained was 27.625 mm Zone of inhibition (ZOI) for gram-negative bacteria, 23.88 mm ZOI for gram-positive bacteria, and a percent blocking of ultraviolet radiation with a value of 99.99% via dip-dry-cure method.
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Various natural resources used for the synthesis of green metal nanoparticles
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Comparative Green Synthesis Using Plants, Bacteria, and Fungi 126
5.5. Hybrid Sustainable Materials
Hybrid sustainable materials for textile functionalization combine natural and synthetic origins, as well as natural with natural origins, designed for sustainability. This combination imparts advanced properties such as antimicrobial, conductive, smart UV-protection, while reducing environmental impact.
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This is achieved by using green methods to create functional fabrics for e-textiles, medical, and industrial uses, balancing performance with biodegradability and circularity.
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The key features of such materials are a balance between sustainability and functionality, making them suitable for eco-friendly applications.
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Hybrid sustainable materials can be obtained from the combination of natural, recycled, mineral, and bio-synthesized metal nanoparticles.
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For example, cotton fabrics were coated with nanostructures of cellulose and lignin. Glycerol and silicone elastomer were applied as binding agents under different coating conditions. These findings demonstrate that wood-derived nanostructures can effectively modify cotton fabrics, combining renewable and synthetic components to create functional and more sustainable textile finishes.
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Figure 11 shows that multifunctional coatings for textiles have been successfully produced via a layer-by-layer deposition technique employing polyaromatic hybrid nanoparticles, enabling enhanced surface functionality. In this work, biobased nanoparticles, produced from natural fatty acid, tall oil fatty acid (TOFA) and lauric acid (La) esterified lignins and waxes, have been used to create multifaceted textile coatings using a layer-by-layer deposition method. The results show that biobased nanoparticle coatings greatly enhance textile performance by raising the water contact angle from 43° to approximately 150°, preserving air permeability of 23-31 mm/s, offering approximately 50% antibacterial inhibition, and keeping hydrophobicity after two washes. Illustration of the layer-by-layer procedure for functionalization of the cellulosic substrates. (A) Photographs of aqueous nanoparticle dispersions and cotton fabrics functionalized with the respective NP dispersions. (B) The NP samples from 1-7 are (1) SWPs, (2) CWPs, (3) La-LNPs100, (4) La-LNPs70, (5) La-LNPs30, (6) TOFA-LNPs and (7) LNPs
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Functionalization of Cotton Fabrics With Mixtures of Nanoparticles and Their Applications 134
6. Main Functionalization Methods
Overview of Textile Surface Functionalization Methods, Process Types, and Key Functionalities
To improve coating adherence and activate textile surfaces without changing bulk properties, sophisticated techniques, including plasma treatment and plasma-induced grafting, are used. 143 Physical and hybrid methods like layer-by-layer assembly, electrospinning, and nanoparticle-based finishing offer high surface area, multifunctionality, and controlled performance. Chemical methods like sol-gel coatings, grafting modification, and surface-initiated polymerization allow the creation of long-lasting and adjustable functional layers. 144 Simultaneously, new sustainable approaches, such as enzymatic functionalization and hybrid combination techniques, have drawn more attention because of their eco-friendliness and capacity to produce long-lasting, multipurpose finishes appropriate for smart and next-generation textile applications. 145 Furthermore, these sophisticated surface modification techniques allow for exact control over surface chemistry and morphology, improving functional finishes’ adherence, durability, and homogeneity. 146 Therefore, it is possible to successfully incorporate multifunctional properties such as UV protection, flame retardancy, hydrophobicity, and self-cleaning behavior without affecting the fabrics’ inherent comfort and mechanical properties. As a result, a crucial strategy for creating long-lasting, high-performing, and sustainable functional textiles for cutting-edge and intelligent applications is the combination of chemical and physical surface modification approaches.
7. Common Functional Properties Achieved
The behavior of these functional textiles is strongly governed by the chemical and physical characteristics of their surface. Progress in understanding this functional behavior is only possible when these characteristics are known, and therefore, surface analysis is a crucial and necessary step.
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With the fast advancement of materials and surface chemistry, as well as the emergence of cutting-edge spinning technology, a wide range of functional textiles has been designed and produced by utilizing the developed functional materials via spinning methods or direct surface modification techniques.8,17 Functionalization of textiles and related materials has enabled a wide range of performance enhancements that enhance safety, comfort, and interactivity. For instance, antimicrobial properties are achieved through the integration of bioactive agents such as silver and zinc-based nanoparticles and chitosan composites to inhibit bacterial growth and maintain hygiene even after repeated laundering cycles, which is critical for healthcare and protective apparel applications.
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Figure 12 shows the schematic illustration of an antibacterial, antifungal and antiviral-treated fabric. The progress of antimicrobial textiles involves various fabrication techniques aimed at integrating antimicrobial agents onto/into textile substrates. These methods ensure that the antimicrobial properties are effectively imparted to the fabrics, enhancing their ability to inhibit microbial growth and proliferation. The primary fabrication methods include surface modification, coating, incorporation during fiber production, and embedding NPs.
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Schematic illustration of an antimicrobial textile
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The other common functional property achieved in textile functional finishing is UV protection, which is typically imparted by incorporating UV-absorbing or scattering material such as plant extracts, oil and nanomaterials such as TiO2 and ZnO NPs into fabrics, significantly increasing their ultraviolet protection factor and extending service in outdoor environments.
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Flame retardancy is achieved through functional coatings and nanocomposite finishes that promote char formation and reduce flammability, with modern research focusing on eco-friendly phosphorus-based and bio-derived flame-resistant systems that also preserve mechanical properties.
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Figure 13 shows that eco-friendly functional properties were achieved on UV-protection and antifungal activities from CuO NPs and A. nilotica algae extracts. Further, hydrophobicity and moisture management are realized via surface treatments or nanostructured coatings that increase water repellency and improve sweat wicking while maintaining breathability, which enhances comfort in performance and protective textiles.
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Conductivity and smart functions have been widely explored in smart and e-textiles, where conductive fibers, sensors, and integrated electronic components allow real-time physiological monitoring, data transmission, and interaction with connected systems, emphasizing wearable health and IoT-enabled textile platforms.
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Furthermore, cosmetic and wellness functionalities are emerging through the controlled delivery of bioactive compounds, aroma-releasing encapsulates, and therapeutic finishes that impart skin-friendly effects and sensory benefits, reflecting an increasing trend toward multifunctional textiles that enhance both performance and well-being
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Antifungal and UV-protective properties of cotton fabric treated with CuO nanoparticles and Acacia nilotica algae extracts
155
8. Environmental, Toxicological, and Life-Cycle Considerations
Balancing functional performance with safety and sustainability is crucial. For example, nanoparticles enhance textile functionality, but they may pose potential environmental and toxicological risks if released into ecosystems or through human exposure. 156 In contrast, plant and animal-derived extracts are biodegradable, safer, and support low-impact life-cycle approaches. 157 Concerns over the eco-toxicity of coating materials, especially those used in multi-functional applications like flame retardancy, antimicrobial protection, and self-cleaning, are becoming increasingly important as their widespread use may result in environmental contamination. Many of the chemicals and compounds incorporated into these coatings, such as silver nanoparticles, titanium dioxide, and certain phosphorus-based flame retardants, have raised concerns about their potentially harmful impact on ecosystems when they leach into water bodies, soil, or air. 158
For example, silver nanoparticles and titanium dioxide (TiO2) are effective in antimicrobial and photocatalytic properties in self-cleaning coatings, respectively; they have an eco-toxicity concern. 159 According to Chandoliya, R. et al., 160 TiO2 nanoparticles can build up in soil and water after being discharged into the environment, impacting microorganisms that are essential for the cycling of nutrients and the health of ecosystems. Additionally, studies indicate that although TiO2’s photocatalytic action is advantageous for self-cleaning, it may unintentionally break down natural organic molecules in ecosystems, leading to unforeseen environmental effects. Furthermore, Copper oxide nanoparticles have exponentially increased in various applications (such as industrial catalyst, gas sensors, electronic materials, biomedicines, and environmental remediation) due to their flexible properties. These broad applications, however, have increased human exposure and thus the potential risk related to their short- and long-term toxicity. 161 The increasing focus on the eco-toxicity of coating materials has prompted efforts to develop more sustainable alternatives in functional finishing of textiles. Bio-based materials derived from natural sources, such as plant extracts, oils and polysaccharides, are being explored to reduce the environmental footprint of coatings. Similarly, nanomaterials with lower toxicity, such as nano chitosan and graphene oxide are being considered for their lower toxicity profiles and enhanced compatibility with natural ecosystems. 162
The toxicological effect of synthetic and some metal nanoparticles functionalizing materials leads to more eco-friendly coatings for the development of “green” alternatives that provide the same or better performance while reducing environmental harm. 163 These include coatings made from renewable resources such as collagen, alginate and chitosan derived from non-toxic, plant-based antimicrobial agents. 164 Chitosan, for example, has shown antimicrobial activity comparable to silver-based coatings but with much lower environmental toxicity. 165 Similarly, bio-inspired coatings, such as those based on natural plant and animal waxes and oils, are being engineered as a renewable and sustainable alternative, but balancing the multifunctionality of coatings with their eco-toxicity remains a key challenge. 166 Sustainable finishing strategies aim to close resource loops via recycling, biodegradation, and reduced chemical footprints with the help of identifying hotspots through life-cycle assessments. 167
9. Challenges and Future Research Direction
Despite the notable progress in sustainable finishing materials and methods, several challenges remain. The selection of the right materials with the right coating method is often a limiting factor, as they may require complex extraction and application processes. 168 The performance and durability of some eco-friendly finishes also do not yet match those of conventional methods, necessitating further research and development. 11 Barriers include balancing sustainability with functional performance, regulatory compliance, supply chain misalignment, skill gaps (the use of the right materials with the right method), inconsistent results, and fabric compatibility are some of the key challenges faced in adopting sustainable finishing processes. 169
Therefore, future research should focus on optimizing extraction and application methods for natural dyes and bio-based finishes, as well as exploring new materials and technologies to enhance the performance of eco-friendly textiles. Exploring these synergistic combinations to achieve multifunctional properties and advanced finishing techniques, such as sol-gel processing and nanoparticle incorporation, should be explored to enhance durability and functionality while ensuring sustainability. Moreover, eco-friendly chemical modifications, such as plasma treatment and enzymatic processing, can reduce the reliance on harsh chemicals as described in Table 8. Collaboration between academia, industry, and policymakers will be crucial in driving the adoption of sustainable practices and addressing the environmental challenges faced by the textile industry. Moreover, this analysis offers a road map for creating next-generation functional textiles that satisfy performance requirements while reducing negative effects on the environment and human health by combining material innovation, environmentally friendly application methods, and sustainability considerations.
10. Conclusion
Sustainable functional finishing represents a transformative pathway for the textile industry, balancing high performance with environmental and health considerations. The integration of bio-based materials, green nanotechnology, and advanced surface modification techniques demonstrates strong potential to replace hazardous conventional chemicals. However, to ensure widespread industrial adoption, further research must focus on optimizing formulations, improving durability, reducing production costs, and validating large-scale applicability. Strengthening collaboration between researchers and industry will be essential to translate laboratory innovations into commercially viable solutions that support sustainability, circular economy principles, and long-term environmental protection.
Footnotes
Acknowledgements
The authors acknowledge the valuable contributions of past and current researchers in the field of textile functionalization. Their pioneering and ongoing work in sustainable materials and eco-friendly finishing technologies has significantly shaped the development and direction of this review.
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Author Contributions
All authors listed have significantly contributed to the development and writing of this article review.
Funding
The authors received no financial support for the research, authorship, and/or publication of this article.
Declaration of Conflicting Interests
The authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.
Data Availability Statement
No data was used for the research described in the article.