Advances in Thermoregulating Textiles: Materials, Mechanisms, and Applications

Abstract

Advancements in thermoregulating textiles have been propelled by innovations in nanotechnology, composite materials, and smart fiber engineering. This article reviews recent scholarly papers on experimental passive and active thermoregulating textiles to present the latest advancements in these fabrics, their mechanisms of thermoregulation, and their feasibility for use. The review underscores that phase-change materials enhanced with graphene, boron nitride, and carbon nanofibers offer superior thermal conductivity, phase stability, and flexibility, making them ideal for wearable applications. Shape-stabilized phase-change materials and aerogel-infused fibers have shown promising results in outdoor, industrial, and emergency settings due to their durability and high insulation efficiency. Radiative cooling textiles, engineered with hierarchical nanostructures and Janus wettability, demonstrate passive temperature regulation through selective solar reflection and infrared emission, achieving substantial cooling effects without external energy input. Thermo-responsive, shape-memory materials, and moisture-sensitive polymers enable dynamic insulation and actuation. Liquid-cooling garments and thermoelectric hybrids deliver precise temperature control but face challenges in portability and power consumption. While thermoregulating textiles show promise, the main challenges include achieving scalable manufacturing, ensuring material flexibility, and integrating multiple functions without sacrificing comfort. Future research should focus on hybrid systems combining passive and active mechanisms, user-centric wearability studies, and cost-effective fabrication methods. These innovations hold significant potential for applications in extreme environments, athletic wear, military uniforms, and smart clothing, contributing to energy efficiency, health, and comfort in a warming climate.

1. Introduction

The human body strives to keep its temperature around 37 °C, with a variation of about ±1 °C. This temperature can vary depending on an individual’s health, physical activity, and environmental conditions [1]. The challenges of thermoregulation are now compounded by rising temperatures linked to global warming. According to the Intergovernmental Panel on Climate Change (IPCC) Sixth Assessment Report (AR6), the average global temperature has risen by roughly 1.19 °C over the past decade (2014–2023) in comparison to levels before industrialization [2]. If greenhouse gas emissions are not significantly curtailed, global temperatures are expected to continue to increase, raising the risk of extreme heat events [3,4]. This warming trend will likely lead to a notable rise in the frequency, intensity, and length of heat waves [5].

Increasing temperatures in the environment diminish the body’s ability to cool itself through processes like sweating and blood vessel dilation. This elevates the likelihood of heat-related health issues, including heat exhaustion and heatstroke, particularly during periods of extreme heat [6,7]. Vulnerable populations such as the elderly, infants, and individuals with chronic health conditions face higher risks due to their bodies’ less effective thermoregulation [8]. The phenomenon of urban heat islands exacerbates this problem in metropolitan areas, making it increasingly difficult for residents to find relief from the heat, especially during nighttime hours [9,10].

At present, centralized heating and cooling systems are commonly used in the interiors of contemporary buildings to ensure thermal comfort. Nevertheless, these systems demand substantial energy to regulate the temperature of entire structures instead of concentrating on targeted areas for body thermal management [9]. The extensive use of energy in residential and commercial structures accounts for about 40% of global electricity usage, posing significant obstacles for environmental sustainability and energy efficiency while undermining the efforts to mitigate climate change [11]. Furthermore, these common heating and cooling systems often do not meet the unique thermophysiological comfort needs of individuals, which can differ markedly from one person to another. Customized thermoregulation refers to the accurate control of temperature within the microenvironment created by clothing as well as the broader macroenvironment of the body and its surroundings [12]. This is crucial for achieving an energy-efficient future while also ensuring individual thermophysiological comfort.

Conventional textiles are often unable to adjust to fluctuating environmental factors like temperature and humidity, causing discomfort in both hot and cold situations [12]. For example, conventional fabrics may fail to properly control heat movement between the body and the surrounding environment, leading to insufficient thermal insulation in cooler weather or too much heat retention when it is warm [13,14]. The unchanging characteristics of conventional textiles have created a demand for innovative and adaptive thermoregulating solutions. Managing heat and moisture effectively is essential for ensuring comfort in the body [15]. Conventional textiles often struggle to achieve a proper balance between heat release and moisture absorption, which results in discomfort and diminished performance across various uses, including athletic and safety apparel [16,17]. Consequently, the development of fabrics that feature responsive thermal and moisture management systems to overcome these issues has emerged as a key area of focus.

These materials, known as thermoregulating textiles, are specially engineered to manage body temperature by responding to variations in both external and internal heat conditions [1]. They can either hold on to heat or release it to ensure thermal comfort, which makes them ideal for use in clothing, bedding, and various applications in the medical and sports fields [16]. Thermoregulating textiles regulate body temperature through a combination of passive and active mechanisms [15]. Passive regulation mainly depends on the natural characteristics of the fabric to control heat and moisture levels. For instance, materials such as wool or fleece capture air pockets to retain warmth, whereas breathable textiles permit moisture vapor to escape, thereby minimizing overheating [18]. An important advancement in passive thermoregulation involves phase-change materials, which can absorb, store, and release heat during their transition from a solid to a liquid form. This mechanism effectively helps stabilize temperature changes and ensures thermal comfort [19].

Active thermoregulation, on the other hand, refers to fabrics that can react to temperature variations through integrated technologies. These smart textiles often feature sensors and conductive threads capable of regulating temperature by providing electrical heating or cooling [20]. Additionally, certain materials utilize shape-memory polymers, which can physically change their form to enhance ventilation or insulation depending on temperature changes. These innovative fabrics allow clothing to adjust immediately to the wearer’s preferences or environmental conditions [20]. An additional key feature of thermoregulating fabrics is their ability to manage moisture. Unique fibers that are either water-attracting (hydrophilic) or water-repelling (hydrophobic) can effectively draw moisture away from the skin and distribute it to the fabric’s surface [16]. This process speeds up evaporation, aiding in cooling and keeping the individual dry. By integrating temperature regulation with moisture management, these textiles enhance comfort, performance, and safety for various climates and activities [12].

While there have been significant advances in thermoregulating textiles, there are few comprehensive reviews on the topic. Recent works have examined the materials utilized in thermoregulating fabrics, including polymeric phase-change materials [19], advanced functional photonic fabric [21], moisture-engineered materials [12], and functional fibrous materials [20]. However, there is a scarcity of reviews that bring together these advancements and explore the mechanisms by which they manage body temperature along with their practical applications. Therefore, this review aims to comprehensively present the latest advances in thermoregulating textiles, discuss the mechanisms underlying their functions, and evaluate their practical applications. By critically evaluating current and emerging practical applications, this work highlights the transformative potential of these materials in enhancing human well-being, energy efficiency, and sustainability across consumer and industrial domains.

2. Methods

This review was conducted to systematically gather, analyze, and synthesize current knowledge on thermoregulating textiles, with a focus on material mechanisms and real-world applications. The literature search was carried out up to April 2025 using major scientific databases, including Web of Science, Scopus, and ScienceDirect. Keywords and keyword combinations used in the search included “thermoregulating textiles”, “phase change materials”, “smart fabrics”, “adaptive clothing”, “moisture management”, “thermal comfort”, and “temperature-responsive materials.”

To ensure relevance and quality, peer-reviewed journal articles, review papers, and high-impact conference proceedings were prioritized. The criteria for inclusion were (1) articles must have been published in the last 10 years; (2) they should focus on thermoregulating materials specifically for textiles or cloth-making, rather than other uses; (3) they need to explain the thermoregulating mechanisms of these materials; (4) they must discuss the practical applications of the materials. Studies that were exclusively theoretical and lacked material validation were excluded, unless they introduced new conceptual frameworks with clear implications for textile design.

The review process followed a thematic categorization, with the literature organized into three primary areas: (1) passive and active thermoregulation mechanisms, (2) materials and fabrication technologies, and (3) feasibility and potential applications across sectors such as apparel, healthcare, military, and building interiors. A critical analysis of the different technologies was conducted based on parameters such as thermal responsiveness, durability, and scalability. Trends and research gaps were identified to inform future development in both scientific and commercial contexts.

3. Passive Thermoregulating Textiles

As global temperatures increase and the need for energy-efficient solutions rises, passive thermoregulating textiles have become a groundbreaking innovation in material science and sustainable fashion. Unlike active systems that depend on external energy sources, passive thermoregulating textiles control heat transfer through their inherent material characteristics and design features [22]. These textiles ensure thermal comfort by utilizing mechanisms like radiation control, moisture management, phase-change materials (PCMs), and microstructural adjustments that adapt to environmental conditions. Their applications span from performance wear and bedding to architectural fabrics and medical textiles, delivering improved comfort, energy efficiency, and versatility.

3.1. Phase-Change Materials (PCMs)

Phase-change materials (PCMs) control temperature by absorbing, storing, and releasing latent heat during phase transitions, which mainly occur between solid and liquid states. When surrounding temperatures exceed a PCM’s melting point, it absorbs excess heat and melts, thus cooling the nearby area (Figure 1) [23]. In contrast, when temperatures fall, the PCM solidifies and releases stored heat, warming the surroundings (Figure 1). This reversible thermal management process allows PCMs to maintain a consistent microclimate around the human body without needing external energy [23]. Recent developments in thermoregulating textiles that use PCMs have greatly enhanced thermal performance, durability, and user comfort.

To improve integration with textiles, PCMs are frequently microencapsulated, which permits their embedding in fibers, coatings, or laminates without risk of leakage during phase changes [24]. Microencapsulation also enhances durability and washability, making these materials better suited for practical applications. De Castro et al. treated textiles with 8 wt% of microencapsulated n-docosane, resulting in a temperature buffering effect of 11 °C during the heating process. When cooled, these treated fabrics exhibited a temperature rise of 6 °C over more than 100 cycles of alternating heating and cooling [25]. Notably, similar thermoregulating characteristics were identified in fabrics that had been stored at room temperature for a duration of 4 years (1500 days). In these aged fabric composites, the temperature buffering effect increased to 14 °C during heating, while the temperature rise during cooling reached 9 °C. Both of these effects remained consistent in the older fabrics, even after 100 heating and cooling cycles [25].

Figure 1. Passive thermoregulating textiles. Modified from [19,26,27,28].

Figure 1. Passive thermoregulating textiles. Modified from [19,26,27,28].

In a separate study, various cotton types (G94, G86, and G86/polyester blends) as well as pure polyester fibers were treated with PCM composites to enhance their thermoregulation capabilities [29]. The yarns underwent treatment with octadecane, which was integrated into alginate stearate and/or pectin stearate. The findings indicated that all yarns treated with the PCM composites exhibited improved thermoregulation properties, evidenced by an increased duration index and increased latent heat compared to their untreated counterparts. Furthermore, yarns coated with the combination of pectin, alginate, and stearic acid demonstrated a greater duration index and greater latent heat than those treated with pectin and stearic acid or alginate and stearic acid as hosting agents [29].

Zeighampour et al. developed a flexible thermal storage textile by integrating polyethylene glycol into carbon nanofibers and reduced graphene oxide nanoparticles. This composite enhanced thermal conductivity by 454% and prevented PCM leakage, maintaining flexibility with a less than 30% change in bending length. The material exhibited phase-change temperatures suitable for human comfort (melting: 30.1–31.4 °C; freezing: 19.2–24.3 °C) and demonstrated durability with less than 4% weight loss after washing and abrasion tests [30]. In a previous study, Yan et al. utilized microfluidic technology to fill a flexible hollow polypropylene fiber with polyethylene glycol 1000, a PCM. The highest filling ratio of this PCM within the polypropylene filament reached approximately 83 wt.% [31]. The heat loss percentages and encapsulation efficiency were recorded at 7.65% and 96.7% for fibers that were as-spun (i.e., fibers immediately after spinning without any further mechanical treatment) and 1.53% and 93.7% for fibers that had undergone post-drawing (i.e., fibers that had been mechanically stretched after spinning), respectively. The weak adhesion of polyethylene glycol to the inner walls of the polypropylene fibers encouraged the formation of bubbles and aggregation at the core–sheath boundary, resulting in distinct crystallization behaviors of the PCM at this interface compared to within the overall PCM matrix [31]. The thermal stability of the polyethylene glycol remained stable when encased in polypropylene. Tests involving cycles of heating and cooling demonstrated the reversibility of latent heat release and storage capabilities, as well as the dependability of the PCM fiber [32].

Liang et al. created a versatile solid-to-solid PCM coating by reacting polyethylene glycol with 3-isocyanatopropyltriethoxysilane to form a highly reactive silanol group, which confers it a self-crosslinking property. This solid-to-solid PCM coating maintained the phase-change characteristics of the unmodified polyethylene glycol while ensuring excellent shape stability [33]. The coating was then applied to polymer textiles integrated with silver nanowires via a scalable dip-coating method. Remarkably, the phase-change textiles demonstrated an electromagnetic interference shielding efficiency of about 72 dB with a thickness of 0.26 mm and possessed an energy storage capacity of 86.6 J g⁻¹. Additionally, the textiles displayed a responsive thermal behavior that included high joule heating efficiency, effective heat dissipation, and outstanding heat retention and release capabilities [33].

A new method entails producing high-enthalpy flexible phase-change nonwovens through the wet spinning of hybrid graphene/boron nitride fibers succeeded by paraffin infusion [34]. These materials realize an enthalpy value of 206.0 J/g, demonstrating remarkable thermal stability and ultra-high water vapor permeability akin to that of cotton. They preserved 97.6% of their thermal cycling capacity after 1000 cycles, rendering them ideal for applications such as smart temperature-regulating clothing and masks [34]. Composite aerogel fibers made of polyimide and boron nitride (PI-BN), characterized by high porosity and strong mechanical properties, have been created through freeze-spinning [35]. These fibers can function as both a pathway for heat conduction and a structural framework for PCMs. To enhance the PI-BN aerogel fabric, polyethylene glycol was introduced into its pores through vacuum impregnation, resulting in a phase-changeable PI-BN/polyethylene glycol textile [35]. The superior thermal conductivity of the PI-BN framework contributes to a rapid thermal response during phase changes, while the aerogel’s high porosity facilitates polyethylene glycol loading and prevents liquid leakage during phase transitions. The final PI-BN/PEG composite textile exhibited notable thermal conductivity (5.34 W m⁻¹ K⁻¹), a high enthalpy of 125.2 J g⁻¹, and exceptional stability throughout 100 heating and cooling cycles, ensuring effective thermoregulation. Additionally, a coating of polydimethylsiloxane has been applied to the surface of the PI-BN/PEG textile, imparting water-repelling properties and washability [35].

Vacuum-impregnating the pores of expanded perlite with eutectic mixtures of capric acid and palmitic acid resulted in a shape-stabilized PCM [36]. This material was then applied to the fabric surface with a polyurethane solution. The latent heat values observed during melting and freezing for the shape-stabilized PCM were 86.57 kJ/kg and 86.19 kJ/kg, respectively. Textiles treated with this material exhibited an increase in freezing enthalpy from 8.93 kJ/kg at 5% shape-stabilized PCM to 44.09 kJ/kg at 25%. Furthermore, thermogravimetric analyses revealed that the composite textile/PCM displayed notable thermal stability. Mechanical testing indicated that the composite at 20% PCM reached the highest tensile strength of 4.96 MPa relative to other composites. Additionally, thermal cycling evaluation showed that the composite at 20% PCM maintained substantial long-term stability, despite experiencing decreases in both melting and freezing enthalpies of 7.4% and 14%, respectively, after undergoing 100 cycles [36]. These findings highlight the significant potential for applications focused on improving thermal comfort in environments such as tents and buildings.

In addition, Lu et al. created a high-performance textile architecture designed to prevent the leakage of paraffin wax as a PCM using a coaxial electrospinning method. This technique resulted in smart textiles featuring a core–sheath design, with the paraffin wax as the core layer and polyacrylonitrile as the outer sheath [37]. To enhance solar energy heat utilization, hexagonal cesium tungsten bronze was integrated into the textiles, offering exceptional absorption in the near-infrared (IR) spectrum. Remarkably, the smart textile encapsulated 54.3% of the PCM (with a latent heat of 60.31 J/g) and maintained its stability well, exhibiting nearly unchanged latent heat even after 500 cycles of heating and cooling [37].

The feasibility of integrating PCMs into textiles has been demonstrated through various innovative methods, including microencapsulation, hollow fiber filling, coaxial electrospinning, dip-coating, and vacuum impregnation [38]. Microencapsulation, in particular, has proven essential for stabilizing PCMs during repeated phase changes, preventing leakage, and improving washability and durability. For instance, de Castro et al. showed that microencapsulated n-docosane retained its thermoregulating function even after 100 heating–cooling cycles and 4 years of room-temperature storage [25]. This level of long-term performance supports the practicality of PCMs in real-life applications like clothing and bedding. Additionally, the use of biopolymers (e.g., alginate, pectin) and synthetic carriers (e.g., stearates) enhances the compatibility of PCMs with various textile fibers, such as cotton and polyester. The findings of Ali et al. demonstrate that such composites improve thermal behavior, increasing latent heat capacity and thermal regulation duration across different fabric types [29].

Recent advances in nanotechnology and composite materials have significantly expanded the capabilities of PCM-based textiles. The incorporation of graphene, carbon nanofibers, and boron nitride into PCM systems [30,34,35] not only improves thermal conductivity but also ensures mechanical flexibility and leakage prevention. These materials support high thermal performance (e.g., up to 206 J/g enthalpy) while retaining user comfort features like breathability and low stiffness. Notably, the PI-BN/polyethylene glycol aerogel textile developed by Zhang et al. exhibited exceptional phase-change stability and hydrophobicity, which are critical for outdoor and industrial apparel [35]. In building and shelter applications, shape-stabilized PCMs based on perlite and fatty acid eutectics have shown promise [36]. These materials offer scalable and efficient thermal buffering for static environments like tents or emergency shelters, with mechanical strength and thermal cycling durability making them suitable for rugged conditions.

Despite their potential, certain challenges remain. Ensuring uniform PCM distribution, avoiding phase separation, and maintaining textile flexibility at high PCM loading levels require careful design. Also, fabrication processes like coaxial electrospinning [37] or microfluidic filling [31] may face scalability or cost barriers for mass production, although their performance outcomes (e.g., over 500 stable thermal cycles and >90% encapsulation efficiency) highlight their promise.

3.2. Radiative Cooling and Heating Materials

Textiles that incorporate radiative cooling and heating materials control body temperature by utilizing thermal radiation, mainly in the IR spectrum. Radiative cooling materials enable the passive transfer of heat from the human body to the surroundings through IR radiation [39]. The primary mechanisms involve the following: (1) Elevated mid-IR emissivity (8–13 µm range), allowing the textile to emit body heat into the colder outer space or environment. This wavelength aligns with the “atmospheric window”, where the Earth’s atmosphere is most transparent to IR radiation (Figure 1). (2) Enhanced solar reflectivity, whereby the material reflects sunlight (particularly near-IR and visible light) to reduce heat absorption from solar radiation, thus sustaining a net cooling effect (Figure 1). (3) Low absorptivity, which minimizes the uptake of environmental heat, keeping the material cool [40].

In contrast, materials designed for radiative heating are intended to absorb and retain IR, thereby warming the body. Their mechanisms include the following: (1) high IR absorptivity/emissivity, where materials exhibit strong absorption in the IR spectrum (particularly between 9 and 12 µm) to capture thermal radiation from the body or surroundings; (2) low solar reflectivity coupled with high solar absorptivity, as certain heating textiles are either dark in color or treated with IR-absorbing nanomaterials (such as carbon black or metallic nanoparticles) to improve solar heat absorption; and (3) low thermal emissivity on the external surface to minimize heat loss, with some textiles featuring IR-reflective coatings (like aluminum or silver nanolayers) to help retain heat close to the skin [41].

In a recent study, Wu et al. introduced a mid-IR spectrally selective hierarchical fabric (SSHF) that exhibits superior emissivity within the atmospheric transmission window, achieved through careful molecular design. This innovative fabric minimizes heat absorption from the environment, boasting an impressive solar spectrum reflectivity of 0.97 due to substantial Mie scattering from its hybrid nano-microfibrous composition [42]. When tested in vertical positions during simulated outdoor urban conditions, the SSHF maintained a temperature that was 2.3 °C lower than that of a typical solar-reflecting material, while also demonstrating excellent properties for wearability [42]. A new type of multilayer silk textile (MST) has been created that showcases exceptional overall performance [43]. This textile boasts an extremely high solar reflectance of 96.5% and an IR emittance of 97.1%. Additionally, it offers safety features, as well as high mechanical strength, air and moisture permeability, washability, resistance to abrasion, hydrophobic surface properties, and ultraviolet (UV) resistance [43]. The MST is capable of achieving an impressive temperature drop below ambient levels of 5.1 °C when exposed to very intense solar radiation of 892.4 W m⁻². It outperforms both commercial silk and cotton textiles, yielding temperature reductions of 6.0 °C and 8.3 °C, respectively, at noon. A hat made from the MST demonstrated better cooling capabilities compared to traditional commercial hats [43].

Miao et al. created a membrane made of hierarchical polyurethane and silicon nitride that features Janus wettability using a scalable electrospinning technique followed by treatment with hydrophilic plasma on one side. This membrane demonstrates an impressive angular-dependent solar reflectance of 91% and an IR emittance from the human body of 93%, leading to a significant temperature reduction of approximately 21.9 °C in direct sunlight and about 2.8 °C at night when compared to conventional cotton [44]. The novel combination of Janus wettability and heat conduction in these hierarchically structured textiles results in minimal sweat production, measured at just 0.5 mL h⁻¹, thereby preventing excessive perspiration that could be harmful [44].

In a different study utilizing silk, Zhu et al. processed the material at the nanoscale using a molecular bonding design coupled with a scalable dip-coating method aided by a coupling reagent. The findings indicate that silk processed in this way can achieve cooling effects below ambient temperatures during the daytime [45]. When exposed to direct sunlight with a peak solar irradiance exceeding 900 W m⁻², the nanoprocessed silk maintained a temperature approximately 3.5 °C lower than the surrounding environment (considering an ambient temperature around 35 °C). Additionally, a simulated skin model coated with such nanoprocessed silk exhibited a temperature decrease of 8 °C compared to natural silk. Notably, the capability for daytime cooling below ambient temperatures was accomplished without sacrificing the silk’s wearability and comfort [45].

In addition, a porous fiber-based textile designed for radiative cooling was created using a process of nonsolvent-induced phase separation combined with scalable roll-to-roll electrospinning [46]. Its single fibers contained nanopores, with their sizes being precisely regulated by adjusting the humidity levels during the spinning process. Incorporating core–shell silica microspheres enhanced the textile’s resistance to UV and improved its superhydrophobic properties. An optimized version of the textile demonstrated high solar reflectivity at 98.8% and atmospheric window emissivity at 97%, achieving a temperature drop of 4.5 °C when exposed to solar intensity of over 960 W·m⁻² and a 5.5 °C reduction at night. For individual thermal regulation, results indicate that the textile can provide a temperature reduction of 7.1 °C compared to exposed skin when under direct sunlight [46].

Cheng et al. synthesized an innovative breathable dual-mode leather-like nanotextile that features Janus wettability and asymmetrical wrinkled photonic microstructures, aimed at enhancing thermoregulation through a single-step electrospinning process. This nanotextile was formed by integrally bonding a hydrophilic cooling layer, made of interwoven fibers, with a hydrophobic photothermal layer, resulting in bilayered wrinkle structures that exhibit outstanding optical characteristics, a gradient in wetting, and distinctive textures [47]. The final product demonstrated notable cooling capabilities (22.0 °C) and heating abilities (22.1 °C) when exposed to sunlight, thus increasing the thermal management range by 28.3 °C compared to standard textiles. Furthermore, it is characterized by excellent breathability, softness, flexibility, and the ability to wick away sweat. Real-world wear trials indicated that the nanotextile can create a comfortable microclimate for the wearer, with temperatures being 1.6–8.0 °C cooler and 1.0–7.1 °C warmer than conventional textiles during varying weather conditions [47].

Spectrally selective fabrics have been engineered with chitosan fibers and silica microparticles (SiO₂) for effective thermoregulation throughout the day using a straightforward wet-spinning process [48]. These textiles not only showcased significant porosity but also delivered impressive solar reflectivity of 82.3% within the solar spectrum (λ: 0.3–2.5 µm) and a high IR emissivity of 95.6% within the atmospheric transparency spectrum (λ: 8–13 µm). Furthermore, the textiles provided excellent comfort due to their inherent properties such as flexibility, breathability, and strength. The cooling effect of these wearable textiles was measured at 95.7 W m⁻² during the day and 103.3 W m⁻² at night. When evaluating thermal performance outdoors, the material showed temperature differences of 11.2 °C and 5.4 °C compared to nylon and cotton, respectively, highlighting its ability for passive radiation cooling [48].

Flexible daytime radiative cooling (PDRC) fabrics are gaining attention for their role in individual thermoregulation. A coating made from poly (vinylidene fluoride-co-hexafluoropropene) (P (VDF-HFP)) was developed, featuring uniformly distributed aluminum oxide (Al₂O₃) micron particles and a nanoporous arrangement. This composite coating allows for the production of flexible PDRC textiles that demonstrate impressive properties, achieving a solar reflectance of 0.95 and an atmospheric window emittance of 0.98, all while maintaining a thickness of just 150 μm. When utilized for outdoor radiative cooling, the flexible PDRC fabric achieved a peak cooling effect of 12.5 °C and 5 °C during the day and at night, respectively. Additionally, the textured composite porous design provided enhanced hydrophobic qualities and resistance to UV radiation in the coating [49].

Pillai et al. explored the use of low-temperature plasma (LTP) to modify the surface characteristics of fabrics to enhance their ability to reflect IR radiation from sunlight [50]. This LTP method is suitable for heat-sensitive textile materials because it operates at a comparatively low temperature of 30 °C. The researchers treated various materials, including standard fabrics and electrospun polyethylene terephthalate surfaces with boron nitride, using tetraethoxy orthosilicate plasma. The treatment resulted in the formation of a reactive plasma-polymerized silane nanolayer on these surfaces. The findings indicated that the nanosurface created by the plasma treatment exhibited greater reflective capabilities for IR rays and maintained a temperature that was approximately 15 °C cooler than the untreated surfaces [50].

Recent studies have demonstrated the technical feasibility of creating textiles with tailored optical properties that align with the “atmospheric window” (8–13 µm) where Earth’s atmosphere permits IR radiation to pass freely. For instance, the mid-IR spectrally selective hierarchical fabric (SSHF) and multilayer silk textile (MST) have achieved solar reflectivity exceeding 96% and IR emissivity above 97%, translating to significant temperature reductions—up to 5.1 °C below ambient temperature under intense solar radiation [42,43]. These achievements are enabled by structural and compositional engineering, including Mie-scattering nanofibers and hybrid nano/micro morphologies. The development of materials with Janus wettability [44,47] further illustrates how fabrics can be tuned to exhibit dual-mode behavior—facilitating both cooling and heating under varying conditions. This dual-mode function significantly expands their usability in real-world settings, particularly in climates with large diurnal temperature variations.

The most immediate applications lie in personal thermal regulation, especially for outdoor workers, athletes, military personnel, and individuals in regions with limited access to air conditioning or heating. Radiative cooling fabrics reduce dependency on energy-intensive air-conditioning systems, supporting sustainability and public health goals amid rising global temperatures. Another promising avenue is smart apparel or adaptive clothing systems. Textiles like the breathable dual-mode nanotextile [47] not only offer substantial heating and cooling capacity (up to ±22 °C) but also maintain critical wearability features such as breathability, softness, sweat-wicking, and mechanical durability. These properties are crucial for integration into everyday clothing without compromising user comfort or mobility. Nonetheless, the main challenges lie in scalability and fabrication complexity, where the materials must be carefully engineered to exhibit selective IR emissivity and absorptivity in the atmospheric window. This complexity could be a barrier to large-scale manufacturing and cost-effectiveness. Furthermore, designing textiles that adaptively perform across different lighting and temperature conditions (e.g., hot days versus cool nights) remains a technical hurdle.

Table 1. Summary of the performances of various radiative cooling and heating materials.

Material	Solar Reflectance	IR Emittance	Cooling Performance	Heating Performance	Reference
SSHF	97%	High (mid-IR selective)	2.3 °C lower vs. typical solar-reflecting textile	N/A	[42]
MST	96.5%	97.1%	−5.1 °C (892.4 W/m2); −6.0 °C vs. silk; −8.3 °C vs. cotton	N/A	[43]
Janus PU/Si3N4 membrane	91%	93%	−21.9 °C (day); −2.8 °C (night) vs. cotton	N/A	[44]
Nanoprocessed silk	>90%	>85%	−3.5 °C (≈900 W/m2); −8 °C on skin model vs. natural silk	N/A	[45]
Porous-fiber textile	98.8%	97%	−4.5 °C (day); −5.5 °C (night); −7.1 °C vs. bare skin	N/A	[46]
Dual-mode nano-leather	N/A	N/A	−22.0 °C (sun)	+22.1 °C (sun)	[47]
Chitosan/SiO2 spectrally selective fabric	82.3%	95.6%	95.7 W/m2 (day); 103.3 W/m2 (night)	N/A	[48]
Flexible PDRC (P(VDF-HFP) + Al2O3)	95%	98%	−12.5 °C (peak, day); −5 °C (night)	N/A	[49]
LTP-treated fabrics	Higher IR reflectivity	N/A	≈15 °C cooler vs. untreated	N/A	[50]

Note: N/A is the abbreviation of not available.

summarizes the performances of the radiative cooling and heating materials discussed above.

3.3. Thermo-Responsive Polymers

The thermo-responsive polymers used in thermoregulating textiles represent advanced materials that alter their properties in response to temperature changes. This capability enables fabrics to adapt to body heat or surrounding conditions, thereby enhancing comfort by regulating heat and moisture levels. These polymers exhibit a critical temperature known as the Lower Critical Solution Temperature (LCST). When the temperature is below the LCST, the polymer exhibits hydrophilicity (attraction to water) and expands (Figure 1) [27]. Conversely, when temperatures exceed the LCST, it transitions to a hydrophobic (repellent to water) state and contracts. In the context of textiles, this transformation influences breathability and heat retention. Cooler temperatures lead to a more open, breathable fabric, while warmer temperatures cause the fabric to shrink, trapping heat (Figure 1) [27].

Liang et al. developed a scalable method for in situ grafting to produce smart textile yarns in two categories: LCST—poly (N-isopropylacrylamide); and UCST (upper critical solution temperature)—poly [N, N-dimethyl (methacryloyl ethyl) ammonium propane sulfonate]. These yarns exhibit contrasting thermo-responsive wetting properties. The resulting smart yarns are characterized by exceptional biocompatibility, mechanical strength, washability, weavability, and whiteness, even after over 60 washes, which is comparable to standard textile yarns [51]. They can operate as separate components or be integrated to create intelligent fabrics that offer adaptive sweat absorption and smart management of temperature and moisture. An innovative textile hybrid that incorporates both smart yarn categories can provide dry contact and temperature control effects of about 1.6/2.8 °C, respectively, in response to fluctuating ambient temperatures [51].

In another study, a thermo-responsive cotton fabric was developed to manage moisture and temperature by employing horseradish peroxidase, acetylacetone, and hydrogen peroxide to initiate a “graft from” polymerization on the surface of the fibers [52]. Thermosensitive monomers, diethylene glycol monomethyl ether methacrylate, and poly (ethylene glycol) methyl ether methacrylate were chosen for the graft copolymerization process. The resulting copolymer demonstrated an LCST of 29 °C. Below this temperature, the cotton exhibited hydrophilic properties, while above it, the fabric became hydrophobic. At elevated temperatures (greater than the LCST), the cotton showed improved air and moisture permeability compared to at lower temperatures (less than the LCST). Additionally, in colder settings, this fabric provided a heat preservation benefit, staying approximately 1.5 °C warmer than untreated cotton fabric [52]. A study adopted a comparable methodology to create a thermo-responsive cotton fabric [53]. This fabric was produced through UV-induced free radical polymerization coupled with a pad-dry-cure technique for grafting the copolymer. It demonstrated a reversible change between hydrophobic and hydrophilic properties, lasting at least 5 cycles and enduring up to 50 rubbing cycles. In contrast to untreated cotton, the fabric exhibited a heating effect of 2.4 °C in cold conditions and a cooling effect of 1.3 °C in warm conditions [53].

Qiu et al. produced a polyester/cotton fabric with a Janus structure showcasing outstanding capabilities in temperature-sensitive moisture and thermal regulation. This was achieved by applying two different temperature-sensitive materials with hydrophobic and hydrophilic properties through a unilateral spray-coating method combined with in situ UV-induced free radical polymerization on a 60/40 polyester/cotton blend fabric [54]. The polymer 2-(2-methoxyethoxy) ethoxyethyl methacrylate was employed to develop an LCST polymer, whereas N,N-dimethyl (methacryloylethyl) ammonium propane sulfonate created a UCST polymer on the fabric’s surface. This fabric exhibited a reversible hydrophobic-to-hydrophilic transition as environmental temperatures fluctuated. The varying hydrophobic and hydrophilic patterns on the fabric resulted in a significant wettability gradient. This enhancement increased the moisture permeability to 6792.5 g/m²·24 h, which is 1132.1 g/m²·24 h higher than that of the unmodified polyester/cotton fabric at 40 °C. Additionally, the modified fabric demonstrated effective temperature adaptation, yielding ~1.2 °C cooling in warm conditions and ~1.0 °C warming in cold environments [54].

A cooling fabric, modeled after the sweating mechanism of skin, has been developed by applying a thermo-responsive hydrogel onto cotton [55]. The resulting composite hydrogel features a porous design and exhibits a hygroscopic capacity of approximately 1.71 g/g, which enables effective heat dissipation through water evaporation. Findings indicate that this material can achieve a cooling effect of around 13 °C in real-world outdoor scenarios. This self-adjusting fabric can efficiently absorb moisture overnight and facilitate cooling by releasing water during the day. Memiş and Kaplan introduced a nanocomposite finishing treatment that incorporates cellulose nanowhiskers (CNWs) and shape-memory polyurethane that is responsive to temperature (SMPU). This treatment was applied to polyester fabric, resulting in a smart fabric that responded to both moisture and temperature. The research indicated that the treated polyester fabric displayed improved perviousness and sweat absorption, responding dynamically to variations in body temperature and relative humidity as well as environmental conditions [56]. Additionally, the treatment enhanced the mechanical properties and performance metrics of the polyester, such as bursting strength and washing durability. The SMPU-CNW nanocomposite treatment presents a promising option for smart sports apparel, offering thermoregulation features that enhance comfort while maintaining desirable mechanical properties and performance standards [55].

Moreover, there has been an increasing interest in developing textiles responsive to multiple stimuli using various approaches. A smart cotton fabric has been developed which features a multiresponsive structure incorporating hierarchically woven copper nanowire and MXene conductive networks. These components are integrated seamlessly into a 3D woven fabric framework, aimed at enhancing personal healthcare and regulating thermal comfort [57]. The sturdy conductive network is reinforced and safeguarded by poly (3,4-ethylenedioxythiophene), an organic conductive polymer, ensuring better adhesion and durability against environmental factors within the 3D interconnected fabric design. This cotton fabric can react in real time to various stimuli, such as heat, light, temperature changes, and pressure, allowing precise recognition and monitoring of human activities. Moreover, the 3D fabric’s porous structure creates significant capillary forces and confines phase-change materials like polyethylene glycol, which demonstrate broad phase transition temperatures, contributing to effective thermal management. With additional encapsulation in transparent fluorosilicone resin, the fabric also shows remarkable self-cleaning properties, exhibiting both water and oil repellency [57].

Thermo-responsive materials have emerged as a promising innovation in the field of smart textiles, particularly in applications aimed at adaptive thermal regulation, moisture management, and enhanced wearer comfort. From a feasibility standpoint, multiple studies have demonstrated not only the functional performance but also the scalability and durability of these thermo-responsive textiles. Liang et al. presented a scalable in situ grafting method to produce LCST- and UCST-based smart yarns with high biocompatibility, mechanical strength, and resistance to washing and abrasion. Their hybrid textile showed measurable thermal modulation (1.6 °C cooling and 2.8 °C warming), validating the practicality of integrating these smart yarns into everyday garments [51]. Similarly, studies by Yang et al. [52] and Xue et al. [53] employed graft polymerization on cotton fabrics using LCST-type polymers, showing stable performance over repeated cycles and significant thermal effects (up to 2.4 °C warming and 1.3 °C cooling). These results suggest that thermo-responsive coatings can be effectively applied to natural fabrics like cotton without compromising softness or comfort while still delivering tangible thermal benefits.

Beyond temperature alone, the integration of thermo-responsive materials with other smart features further enhances the versatility of textiles. Ji et al. developed a cotton-hydrogel composite mimicking the human skin’s sweating mechanism, offering up to 13 °C of cooling in outdoor conditions [55]. Meanwhile, Memiş and Kaplan introduced a nanocomposite treatment using shape-memory polyurethane (SMPU) and cellulose nanowhiskers to create textiles that are responsive to both moisture and heat [56]. The development of multifunctional textiles, as described by He et al., showcases the future potential of thermo-responsive fabrics [57]. However, since thermo-responsive polymers operate based on a specific LCST or UCST, ensuring this transition occurs precisely within the narrow thermal range of human comfort is difficult. While some studies report the fabrics surviving over 60 washes, maintaining long-term functionality such as thermal responsiveness and mechanical strength remains an issue [51].

3.4. Aerogels and Porous Insulating Materials

Aerogels and porous insulating materials act as thermoregulating textiles by utilizing their distinct microstructure and thermal properties to regulate heat flow and sustain thermal comfort [28]. Aerogels are ultralight materials created by substituting the liquid component of a gel with gas (usually air), resulting in a highly porous network (up to 99.8% air). Similarly, porous insulating materials contain voids or pores that capture air or other gases within the fabric. The nanoporous structure retains body heat and prevents its loss to the colder external environment (Figure 1) [28,58].

Xue et al. engineered lightweight polyimide aerogel fibers with exceptional thermal insulation through a process called freeze-spinning, utilizing polyvinyl alcohol to regulate pores. The strong affinity of polyvinyl alcohol for water facilitates quicker ice crystal formation and pore development, and fosters a regulated porous structure within the polyimide aerogel fiber [59]. The resulting polyimide aerogel fiber features significantly smaller pore sizes and an elevated porosity of 95.6%, as well as enhanced flexibility and mechanical strength, making it suitable for fabric weaving. Furthermore, the polyimide aerogel fabric demonstrates low thermal conductivity and outstanding thermal insulation across a broad temperature range, from −196 to 300 °C [59].

Wu et al. developed an aerogel fiber that is enveloped in a flexible layer, resembling the core–shell structure found in polar bear fur. Remarkably, this fiber maintained an internal porosity exceeding 90% while being capable of stretching at up to 1000% strain, a significant enhancement compared to conventional aerogel fibers, which can only stretch by about 2% [60]. The fiber was not only washable and dyeable but also exhibited impressive mechanical strength, preserving its thermal insulation properties even after enduring 10,000 stretching cycles at 100% strain. A sweater made from this fiber was only one-fifth of the thickness of a down sweater, yet it offered comparable performance [60]. Additionally, Li et al. combined the wet-spinning method with freeze-drying to produce robust polyimide aerogel fibers using organo-soluble polyimide. Their distinctive “porous core–dense sheath” structure conferred these fibers exceptional mechanical characteristics, achieving an unprecedented tensile strength and initial modulus of 265 MPa and 7.9 GPa, respectively, at a maximum elongation of 65% [61]. Additionally, the polyimide aerogel fibers exhibited significant porosity (over 80%) and a substantial specific surface area (464 m²/g), equipping the woven fabrics with outstanding thermal insulation capabilities across a broad temperature spectrum of −190 to 320 °C, making them suitable for thermal insulation in extreme environments [61].

A scalable method of producing polyimide aerogel fibers was also achieved through an in situ polymerization process combined with wet-spinning techniques, using monolayered Ti₃C₂T_x flakes as pore-forming agents [62]. The strong interfacial interactions between the MXene and the macromolecular chains contributed to the formation of hierarchical porosity within the composite aerogel fibers, which resulted from the entrapment of the polymerized polyamic acid/Ti₃C₂T_x networks while separating the liquid and solid phases. Consequently, the polyimide/Ti₃C₂T_x aerogel fibers exhibited highly improved mechanical properties (with a tensile strength of 26 MPa), a high specific surface area (145 m² g⁻¹), excellent fire resistance, and outstanding thermal insulation capabilities (illustrated by a low thermal conductivity of 36 mW m⁻¹ K⁻¹) [62]. These properties enable their easy integration into flexible textiles designed for effective thermal regulation applications.

Sai et al. synthesized resilient fibrous silica/bacterial cellulose (BC) composite aerogels by infusing silica sol into a fiber-based matrix created by slicing the BC aerogel, followed by a secondary shaping procedure to produce a composite wet gel fiber featuring a nanoscale network structure [63]. The resulting aerogel fibers demonstrated a tensile strength of up to 5.4 MPa, which can be attributed to the significant increase in the density of BC nanofibers within the matrix due to the secondary shaping technique. Furthermore, these composite aerogel fibers exhibited a high specific surface area of up to 606.9 m²/g, a low density below 0.164 g/cm³, and exceptional hydrophobic properties. Notably, they showcased impressive thermal insulation capabilities in extreme temperature conditions, ranging from 210 °C to −72 °C. Additionally, the thermal stability of these composite aerogel fibers (with a decomposition temperature nearing 330 °C) surpassed that of natural polymer fibers [63].

A separate investigation successfully produced SiO₂/polyimide/aramid fiber aerogel composite fabrics through the integration of coating technologies and finishing processes [64]. This involved using tetraethoxysilane as the precursor, polyimide powder as a reinforcing component, and nonwoven aramid fiber as the base layer. The findings indicated that these composite fabrics demonstrated outstanding performance, significantly inhibiting heat transfer. Additionally, the thermal conductivity at the front reduced from 4.08 to 3.91 (W/cm·°C) × 10⁻⁴ [64]. Drawing inspiration from the fibrous structure of animal hides, a type of porous hierarchical fiber has been created through wet spinning [65]. The resulting biomimetic material showcased low thermal conductivity close to that of cowhide at 0.07 W/mK as well as remarkable mechanical strength reaching 10 MPa, exceptional flexibility, and hydrophobic characteristics [65]. Combining it with a phase-change material allows the fabric to simulate the function of body fat. The combination effectively diminishes heat transfer and reduces surface temperature, emulating the insulation system seen in living organisms.

A scalable method for producing flexible and durable aramid nanofiber aerogel fibers involves continuous wet spinning combined with rapid air-drying. This process utilizes calcium ions for cross-linking and low-surface-tension solvents for solvent displacement, which together improve structural strength and decrease capillary forces during evaporation, thereby limiting shrinkage to 29.0% while enhancing the specific surface area of the fibers to 225.0 m² g⁻¹ [66]. Notably, the air-dried fibers demonstrate high tensile strength (13.5 MPa) and toughness (7.0 MJ m⁻³), which facilitates their integration into textiles. The resulting textile, characterized by a skin–core porous structure, shows low thermal conductivity (about 38.5 mW m⁻¹ K⁻¹) and exceptional thermal insulation over −196 to 400 °C [66]. In addition, Chen et al. developed flexible, high-strength (20.8 MPa), biodegradable holocellulose nanofibrils/cellulose aerogel fibers with a specific surface area of 413 m²/g and porosity of 85% [67]. This was achieved on a large scale using a nano-hybrid strategy along with a simple wet-spinning method. The smart textile made from the fibers demonstrates remarkable self-cleaning and thermal insulation properties across a broad temperature range. When combined with carbon nanotubes, the smart textile displays exceptional capabilities in thermoregulation and sensing for body fluids, human activity, humidity, and temperature, in addition to providing electromagnetic interference shielding effects [67].

Recent advancements in fabrication techniques have significantly improved the feasibility of aerogel-based fibers in textiles, enhancing their mechanical properties, flexibility, and scalability. Traditionally brittle, aerogels now feature high tensile strength and elongation of up to 1000% due to innovations like the freeze-spinning of polyimide aerogels [64] and core–shell structured fibers [60]. Scalable production methods, including wet spinning, freeze-drying, and in situ polymerization [62], make large-scale production viable using cost-effective and biodegradable materials like holocellulose nanofibrils and aramid fibers [66,67]. Aerogel-based textiles offer impressive thermal conductivity values ranging from 0.036 to 0.07 W/m·K, providing insulation comparable to traditional materials while being lighter and thinner, with an operating temperature range of −196 °C to over 400 °C. This indicates that they can provide insulation over a wide temperature range while ensuring comfort and flexibility. Additionally, these fibers exhibit multifunctional properties, including self-cleaning, hydrophobicity, biodegradability, electromagnetic shielding, and sensor integration, making them suitable for smart textile applications. Given their improved qualities, these materials are ideal for outdoor and severe weather clothing, military and aerospace textiles (capable of withstanding a wide temperature range), everyday apparel (offering flexibility, washability, and dyeability), and smart wearables (integrating carbon nanotubes and sensor-responsive capabilities). Notably, aerogel and porous materials also show great potential for biomimetic textiles. Despite the potential, it should be noted that aerogels are traditionally brittle and require special treatments to enhance their strength, which could pose challenges to their scalability and cost-effectiveness for textile applications. Maintaining structural integrity and thermal insulation performance after repeated use, washing, or exposure to environmental conditions can be difficult.

3.5. A Comparative Overview

Thermoregulating textiles incorporate diverse materials to manage body temperature through passive mechanisms. PCMs regulate heat by absorbing or releasing latent heat during phase transitions, offering effective cooling and heating (up to ±14 °C), though high loadings can reduce flexibility and breathability. Radiative cooling and heating materials function by controlling infrared radiation—emitting or absorbing body heat. These materials are highly breathable and washable, with significant cooling potential (up to 21.9 °C), but they could be less effective at night and may have esthetic limitations.

Thermo-responsive polymers change their structure with temperature shifts, modulating moisture and air permeability. They are effective in daily wear and sportswear but depend on precise temperature thresholds (LCST/UCST) and may degrade over repeated use. Aerogels and porous insulators offer exceptional thermal insulation across extreme temperatures (−196 to 400 °C) by trapping air within nanopores. While traditionally brittle and less breathable, recent advancements have improved their flexibility and integration with textiles. All four material types operate without external energy input and have seen significant progress in scalability and textile compatibility. Each suits specific applications, from outdoor gear and emergency wear to smart clothing, based on their thermal performance, durability, and comfort. However, trade-offs exist, such as leakage in PCMs or limited breathability in porous materials.

Table 2. Comparison of the working mechanisms and performances of passive thermoregulating textiles.

Criteria	PCMs	Radiative Cooling and Heating Materials	Thermo-Responsive Polymers	Aerogels and Porous Insulating Materials
Working mechanism	Stores/releases latent heat via phase change (solid ↔ liquid); regulates temperature by absorbing/releasing heat	Controls heat via IR radiation: radiative cooling (emits body heat) or heating (absorbs/retains IR radiation)	Changes between hydrophilic and hydrophobic states based on temperature (LCST/UCST), modulating breathability and moisture retention	Traps air/gases within nanoporous structures to reduce heat transfer and provide insulation
Energy requirement	Passive (no external energy); responsive to environmental temperature	Passive (uses ambient light/heat); does not require external power	Passive; relies on ambient or body temperature changes	Passive; utilizes physical structure, no external energy needed
Cooling/heating performance	Effective; can buffer up to 14 °C (cooling) and rise by 9 °C (heating); maintains temperatures for prolonged periods	Cooling up to 21.9 °C (extreme solar conditions); temperature drops of 4–8 °C typically observed	Moderately effective; ~1.0–2.8 °C heating/cooling; up to ~13 °C in composite hydrogel-based systems	Effective insulation over a wide range (−196 to 400 °C); comparable to down or fat-based insulation
Durability	High: >100–1000 thermal cycles; performance sustained over 4 years; resistant to washing and abrasion	High: Washable, UV-resistant, hydrophobic; retains function after repeated exposure to sun/wear	Proven washability (e.g., >60 washes); some wear-off over cycles; mechanical properties can degrade	High: Very high mechanical strength, flexibility, stretchability (up to 1000%); survives extreme conditions and strain cycles (e.g., 10,000 cycles)
Scalability/manufacturing feasibility	Variable: some methods (e.g., microfluidic, coaxial electrospinning) are complex; others, like dip-coating or vacuum impregnation, are scalable	High: Many radiative materials use scalable techniques (e.g., roll-to-roll electrospinning, dip-coating, self-assembly)	High: Scalable grafting methods (e.g., in situ, UV polymerization); compatible with cotton and synthetic blends	High: Improved with wet spinning, freeze-drying, in situ polymerization; recent developments allow large-scale production with biodegradable, low-cost materials
Comfort and breathability	Improved via nanomaterials/aerogels, but high PCM load can reduce flexibility/breathability	High: Nanofibrous and porous structures enhance breathability, air/moisture permeability, and wearer comfort	High: Designed to modulate moisture/air permeability dynamically; good compatibility with natural fibers like cotton	May limit breathability depending on fiber structure; newer core–shell and porous structures improve comfort
Integration with textiles	Microencapsulation, core–sheath fibers, dip-coating, etc.; compatible with cotton, polyester, etc.	Nanofibers and coatings applied to silk, cotton, polyurethane, and synthetic fabrics	Can be grafted directly onto cotton, polyester, blended yarns; compatible with weaving/knitting processes	Integrated as fibers into yarns or fabrics (e.g., polyimide, aramid, cellulose aerogels); compatible with weaving and coating processes
Leakage risk	Can be an issue (liquid PCMs), but can be mitigated via microencapsulation, core–sheath design, solid-to-solid PCMs	No leakage; materials are solid-state or vapor-based systems	Low; polymers are chemically bonded or grafted onto fabric surfaces	Low; typically dry-state solid structures; minimal risk compared to PCMs
Cost and material availability	Moderate to high: PEG, paraffin, and composite carriers vary in cost; nanomaterials increase cost	Varies: Metal oxides, silica, and carbon-based coatings may increase costs, though mass production could reduce them	Moderate: Uses commonly available monomers/polymers; increasing feasibility	Traditionally costly and brittle but now cost-effective due to scalable methods and the use of abundant natural polymers
Best use cases	Outdoor clothing, sportswear, bedding, emergency blankets, smart textiles for thermal comfort	Daytime wear, desert or urban applications, hats, summer apparel, building materials for passive cooling	Sportswear, daily wear, smart clothing, adaptive clothing, moisture management	Extreme environments (space, arctic, firefighting), outdoor gear, thermal underwear, multifunctional smart textiles
Limitations	Leakage risk in liquid PCMs, phase separation, and stiffness at high loadings; some methods are not yet cost-effective for mass production	May not retain heat effectively at night; cooling is more effective than heating; visual appearance may be limited	Requires precise LCST/UCST matching to user comfort; performance may decline with repeated washing or abrasion	Historically brittle; breathability can be a concern; thermal insulation may not be actively responsive like smart polymers

provides a comparison of their performance.

4. Active Thermoregulating Textiles

Active thermoregulating textiles are advanced materials designed to dynamically respond to changes in temperature by adjusting their thermal properties in real time [68]. Unlike passive textiles, which only insulate or wick moisture, active thermoregulating fabrics can actively regulate heat through mechanisms such as shape-memory polymers or embedded electronic systems. These textiles can either store and release heat as needed or use sensors and actuators to maintain a stable microclimate around the wearer [68]. Active thermoregulating textiles have received less research attention compared to passive ones.

4.1. Shape-Memory Fabrics

Active fabrics can flexibly respond to environmental stimuli, showing a broad prospect in intelligent thermal moisture management. Among them, shape-memory active fabrics can sense external stimuli and make corresponding changes in morphological/fabric structures, presenting outstanding advantages (Figure 2). Shape-memory alloys (SMAs) represent a unique category of materials that can remember their original shape when exposed to specific stimuli like changes in temperature or magnetic fields [69]. Typically composed of a combination of two or more metals, the shape-memory function of these alloys originates from the phase changes between their thermoelastic and martensitic forms [70]. At elevated temperatures, the stable structure is austenite, while the martensite structure prevails at lower temperatures. Upon heating, SMAs contract and transition to the austenite structure, effectively regaining their original configuration. Conversely, during cooling, they gradually revert to the martensite state. SMAs can change shape when forces are applied, but they return to their original form once the memorization process between the two transformation phases is triggered (Figure 2) [69]. Among these, NiTi (nickel/titanium)-based SMAs are particularly prevalent and have found applications in the textile industry [71,72].

Drawing inspiration from responsive hair that either stands erect or flattens in varying temperatures, Choe et al. presented a smart reconfigurable hairy skin created from SMP-based composite arrays (polylactic acid (PLA)/thermoplastic polyurethane (TPU)/graphene oxide (GO)) featuring dynamically adaptable thermal insulation. This innovative skin can adjust its thermal insulation by over 61.4% through the reversible configuration of hairs in response to temperature changes, indicating significant potential for applications in smart clothing or wearable technology [75]. It comprises porous pillar arrays resembling hair, which achieve tunable thermal insulation that decreases when the hairs lie flat and recovers when they stand up, all of which can be attributed to the shape-memory abilities of the SMP arrays. This behavior is elucidated by the microscopic structure of the micro/nanoporous hairs, which can transition from an open-pore condition to a closed-pore condition during the shape-memory effect, facilitating controllable insulation [76].

Due to the limitations of fabrics made from one-way SMPs, those developed using two-way SMPs are considered more advantageous. Roach et al. created innovative smart textiles utilizing liquid crystal elastomer (LCE) fibers that possess reversible shape-memory capabilities. The LCE fibers, which are soft and lengthy, were produced through direct ink writing and showcased a reversible actuation strain of as much as 51% [77]. Subsequently, these fibers were integrated into various smart textiles through knitting, sewing, and weaving techniques. For instance, a cylindrical knit textile was constructed by stitching the LCE fibers along the edge of the cylinder. Upon heating to approximately 120 °C, this cylinder constricts and then expands to room temperature upon cooling, achieving a notable diameter change of 40% [77].

While certain two-way SMP materials are capable of a two-way shape-memory effect, they are not sensitive enough to the small temperature changes around the human body. By comparison, water/moisture-responsive shape-memory materials are appropriate candidates because they can be activated by ambient moisture or human sweat, showing more flexibility, which would be well-suited for wearable applications and thermal moisture management of the human body [78]. Zhong et al. introduced clothing utilizing a Nafion polymer that responds to thermal and moisture changes (a perfluorosulfonic acid ionomer). Nafion is composed of both hydrophobic polytetrafluoroethylene and hydrophilic -SO₃H chains. When it absorbs water, it experiences microphase separation, resulting in a swelling phenomenon. As a result, Nafion material takes in water and bends toward areas of lower humidity in less than one second [79]. Sroysee et al. created two forms of bendable smart clothing that respond to humidity for thermal insulation. The first design mimics human sweat pores with Nafion films and flaps. When temperatures rise and the wearer sweats, the Nafion flaps expand and bend upward, creating openings that promote rapid evaporation of sweat and the release of heat [80]. Conversely, when the temperature drops and humidity declines, the equilibrium of swelling closes these openings, helping to retain heat. This process can occur repeatedly over numerous cycles, indicating excellent stability [80]. The second design features Nafion ribbons that change thickness and serve as inserts. When humidity rises due to perspiration, the Nafion ribbons swell, decreasing the thickness between the layers, which improves thermal conductivity and facilitates heat loss. When sweating ceases, the ribbons quickly revert to an arched shape, leading to reduced air thermal conductivity that helps prevent heat loss [80].

In a study by Mu et al., a self-adaptive actuator system inspired by kirigami techniques was developed for managing body heat and humidity. This system leverages the vapor-absorbing properties and nanoscale molecular channels of Nafion [81]. As it absorbs more vapor molecules, the expansion of the nanochannels is enhanced, resulting in asymmetric expansion on either side of the Nafion film. This creates interfacial stress, which induces bending motion. To capitalize on this property, a kirigami-inspired actuator featuring a semilunar pattern on its surface was created using laser cutting and patterning techniques, allowing it to be easily incorporated into a shirt. During physical activity, for instance, as skin humidity increases, the semilunar patterns curl outward, expanding the openings of the channels and improving heat and humidity management. Compared to conventional textiles, wearing the actuator-enhanced smart shirt helps maintain a lower humidity and temperature on the skin, thereby enhancing thermal and moisture comfort [81].

Additionally, Wang et al. created biohybrid wearable devices that utilize the water-absorbing properties of microbial cells. These devices are designed to react to perspiration while in motion. They developed a sandwich-like structure where layers of cells are applied on both sides of a material that does not absorb moisture, enabling it to respond to variations in localized moisture across the film [82]. This structure alters its shape in reaction to sweat production during physical activity. Furthermore, they engineered sports garments equipped with ventilated flaps that can automatically modify moisture transfer and thermal resistance by adjusting skin exposure levels. The flaps of the apparel transition from a flat configuration before exercise to a curved one after, allowing for adjustable skin exposure, which aids in better temperature regulation in response to the body’s changing conditions [82].

Artificial muscles are innovative materials that can change shape by expanding, contracting, or rotating in response to various external factors, including electric fields, humidity, light, magnetism, and temperature [73]. They hold promise for use in biomedical applications, smart actuators, soft robotics, and advanced textiles. Peng et al. created a scalable, hierarchical structure of artificial muscles using viscose fibers and showcased its application in smart textiles for thermoregulation. They introduced a hot-drawing technique to improve the alignment of the fibers’ microstructure, leading to the formation of double-helical yarn muscles through twisting and plying [83]. The actuation mechanism arises from a cross-scale architecture that includes nano-sized crystals, amorphous structures, and larger spatial helices measuring millimeters. When exposed to moisture, the absorption of water disrupts the hydrogen bonds, resulting in the contraction of the fiber’s length. Conversely, when the fibers dry, the desorption of water allows for the re-establishment of hydrogen bonds, facilitating the fiber’s recovery [83]. A garment featuring water-responsive switchable pores was also developed, demonstrating its thermoregulating capabilities. In dry conditions, the sleeve expands to provide warmth, while in high humidity, it contracts to allow sweat evaporation and heat dissipation [83].

The feasibility of SMFs lies in the successful integration of shape-memory materials, including SMAs, SMPs, LCEs, and moisture-responsive materials such as Nafion or biologically inspired systems. SMAs, particularly Ni-Ti alloys, are known for their reversible phase transformation between martensite and austenite with temperature changes. Their reliability and strength make them suitable for wearable structures, but their high cost, density, and stiffness may limit common use [69,70]. SMP fabrics, such as those by Choe et al., offer lightweight, adjustable thermal insulation. The dynamic restructuring of hair-like components mimics nature, proving responsive design feasibility in textiles [75]. However, traditional SMPs often have one-way memory behavior, limiting adaptability. Two-way SMPs, especially LCEs, show promise due to their reversible properties. Roach et al. integrated LCE fibers into knitted structures for significant deformation and recovery at relevant clothing temperatures, though some need high activation temperatures (~120 °C), which are impractical for wear [77].

Moisture-responsive materials like Nafion and microbial biohybrids offer feasible solutions for wearable applications. Their ability to actuate with minor humidity or sweat fluctuations provides low-energy, biocompatible responsiveness with rapid reaction times and high cycling stability [78,79]. Recent innovations like kirigami-inspired actuators [81] and biohybrid flaps [82] demonstrate the scalability and adaptability of shape-changing components that can be embedded into garments using common fabrication techniques like laser cutting or lamination. Nonetheless, these materials could be difficult to mass-produce and prone to delamination or wear and tear. Additionally, many shape-memory materials (e.g., shape-memory alloys like NiTi or two-way shape-memory polymers like LCEs) require relatively high activation temperatures to trigger their shape transformation.

Table 3. Summary of the performances of various shape-memory fabrics.

Material	Stimulus	Actuation Performance	Activation Conditions	Durability/Cycles	Key Benefits	Ref.
SMP-based composite arrays	Temperature	Thermal insulation change ≈ 61.4% (hairs stand vs. lie flat)	ΔT across body comfort range	Not specified	Fast, reversible tuning of insulation via micro-hair morphology	[75]
LCE fibers (two-way SMP)	Temperature	Reversible actuation strain of up to 51%; cylinder diameter Δ ≈ 40%	Heating to ~120 °C/cooling to root temperature	Reversible over many heating/cooling cycles	Large, reversible shape change built into textile structure	[77]
Nafion bending film	Moisture (humidity)	Bends toward lower-humidity side in <1 s	Ambient moisture/sweat uptake	Rapid, repeatable	Ultra-fast moisture-driven actuation without external heating	[79]
Nafion “sweat-pore” flaps	Humidity	Flaps open/close to modulate evaporation	Wearer’s sweat/decreased humidity	Excellent stability over many cycles	Sweat-responsive ventilation for dynamic thermal comfort	[80]
Nafion ribbon inserts	Humidity	Thickness decreases when wet, causing higher thermal conductivity; reverses when dry	Wearer’s sweat/drying	≥50 rubbing cycles demonstrated	Adjustable thermal conductivity via reversible ribbon geometry	[80]
Kirigami-inspired actuator	Moisture (vapor)	Semilunar cuts curl outward with increased humidity, opening vents	Skin humidity increases	Not specified	Integrated vents that autonomously open/close for heat and moisture	[81]
Biohybrid microbial-cell flaps	Sweat	Ventilated flaps shift from flat to curved for adjustable skin exposure	Physical activity, e.g., induced perspiration	Not specified	Self-powered moisture-actuated flaps for sports garments	[82]
Artificial-muscle yarns	Moisture	Fiber contraction on wetting/extension on drying	Ambient humidity changes	Not specified	Switchable pores in garment sleeves: expand in dry conditions, contract in humidity	[83]

summarizes the performances of the shape-memory fabrics discussed above.

4.2. Other Active Thermoregulating Fabrics

Other active thermoregulating fabrics include thermoelectric and liquid-cooling textiles. Thermoelectric textiles rely on thermoelectric materials that can either convert body heat into electricity (the Seebeck effect) or use electricity to produce heating or cooling (the Peltier effect) (Figure 2). These effects are harnessed using flexible, textile-compatible materials for active thermal regulation (Figure 2) [74]. Liquid-cooling textiles work by circulating a coolant through flexible tubing or channels embedded within the fabric [84]. These textiles actively remove excess body heat, providing a cooling effect. A thermoregulatory textile incorporating advanced radiative electrochromic fibers that can be produced at scale has been fabricated. This textile is designed to operate with low voltage, enabling it to achieve a regulated emissivity of approximately Δɛ ≈ 0.35 [85]. The combination of an outer electrode and a layer of electrochemically adjustable carbon nanotubes provides remarkable electrochemical control over fibers that extend 100 m, achieving this within just 5 s due to reduced internal resistance as the length increases [85]. Consequently, this innovative textile effectively minimizes significant temperature fluctuations, maintaining temperature stability to within about 1.6 °C for simulated skin, which is a marked improvement compared to traditional textiles, which experience variations of about 2.9 °C, even with an ambient fluctuation of 11.2 °C [85].

Fine copper, which is sensitive to temperature, was incorporated into two sections of flexible fusible interlining fabrics utilizing a straightforward thermal bonding technique [86]. This process resulted in the creation of flexible heating fabrics capable of temperature sensing (FHF-TPs). By decreasing the spacing between copper wires and reducing the applied voltage, as well as enhancing the thermal conductivity of the bonding fabric, it is possible to elevate both the heating temperature and the rate of heating. Additionally, this approach minimizes the temperature gradients, resulting in the fabric maintaining a relatively uniform temperature. Furthermore, in a garment heating simulation, the pre-set temperature of the FHF-TPs demonstrated a strong linear correlation with the power consumption in colder environments. After enduring 240 h of aging at temperatures of 80 and 100 °C and being washed 30 times, the mechanical properties of all FHF-TP samples showed no significant changes. With their consistent electrical properties, mechanical integrity, and thermal performance, FHF-TPs are expected to have promising applications in the field of active warming garments [86].

Wang et al. described the production of tri-component elastic-conductive composite yarns (t-ECCYs). This yarn exhibited a quick thermal response and maintained a consistent surface temperature across different voltages and strain conditions. Its stability was validated through alternating voltage on–off cycles [87]. Both static and dynamic performance tests highlighted its ability to deliver targeted and uniform heat to clothing. Findings revealed that knit fabrics enhanced with t-ECCYs were not only effective for applications like localized heating and display features but also demonstrated strong cyclic stability, showing minimal degradation in their functional characteristics after 50 cycles of expansion and release tests [87].

Chai et al. introduced innovative thermoregulating clothing featuring temperature-responsive body heat management, which regulates heat via multiple mechanisms, including convection, sweat evaporation, and radiation. This clothing can autonomously adjust to temperature fluctuations (ranging from 15 °C to 35 °C) within seconds by integrating specially designed metalized polyethylene actuators, which are mechanically and IR-optically enhanced, into the fabric [88]. Thermal manikin evaluations and thermophysiological simulations indicate that this clothing can extend the comfort range by over 2 °C at both ends of the temperature spectrum, leading to approximately 30% energy savings in indoor settings [88]. A liquid-cooling garment (LCG) was specifically designed for automobile users [89]. Silicone tubing, featuring an inner diameter of 0.5 mm and a total length of 71.5 m, was incorporated into a T-shirt design, serving as heat-exchange conduits in eleven distinct areas, including the chest and abdomen. An active cooling system using a thermoelectric cooler with a maximum refrigeration efficiency of 0.68 was implemented, while the LCG’s overall energy consumption peaked at 0.15 kWh [89]. To validate the simulation outcomes, temperature measurements were taken in an outdoor parking area during summer. Experimental findings revealed that the maximum temperature difference between the individual wearing the LCG and the control group reached 3 °C in a high-temperature setting (37–42 °C) [89].

Efforts have also been made to integrate thermoelectric properties with liquid-cooling technologies. An innovative thermoelectric LCG was introduced to enhance the portability and effectiveness of cooling apparel [90]. This cooling system employs a semiconductor chilling plate as its cooling mechanism. When an electric current passes through a thermoelectric conductor, charge carriers move heat from one end to the other, causing one end to heat up while the opposite end cools down. A specific cooling temperature of 6.6 °C/kg was determined to evaluate the overall efficiency of the LCG, representing a notable advancement compared to earlier cooling garments. To understand how ambient temperature and the temperature on the hot side of the cooling unit affect the garment’s cooling efficiency, human trials were conducted. The findings indicate that both the surrounding temperature and the hot-side temperature of the cooling unit negatively impact the cooling performance of the LCG [90].

Liquid-cooling textiles are highly effective and technically feasible, particularly for targeted cooling in high-heat environments [89]. However, they face scalability and power efficiency challenges, which could be mitigated by hybridizing them with thermoelectric materials and improving miniaturization [90]. Compared to other active thermoregulating fabrics, LCGs are more powerful in direct cooling, though bulkier and more complex. As energy-efficient designs and integration techniques improve, liquid-cooling textiles are poised to perform niche but critical roles in wearable thermal management.

5. Conclusions

Recent advancements in thermoregulating textiles—ranging from PCMs and thermo-responsive polymers to radiative cooling structures and liquid-cooling garments—demonstrate both remarkable functional capabilities and growing real-world feasibility. The incorporation of nanomaterials, such as graphene, boron nitride, and carbon nanofibers, has significantly enhanced thermal conductivity, mechanical integrity, and stability in PCM-based systems, enabling multifunctionality and comfort without compromising energy efficiency. Similarly, dual-mode radiative textiles and aerogel-enhanced fibers have proven effective in extreme conditions, offering insulation and passive temperature control while maintaining breathability and flexibility.

However, the field faces ongoing challenges. Key limitations include achieving uniform PCM dispersion without sacrificing textile flexibility, scaling up advanced fabrication techniques such as coaxial electrospinning or microfluidic encapsulation, and balancing functionality with user comfort in shape-memory and liquid-cooling garments. Active systems, like hybrid thermoelectric/liquid-cooling garments, demonstrate high performance but remain bulky and energy-intensive, limiting widespread adoption. Shape-memory alloys, while robust, are still hindered by cost and limited wearability.

For future research, three main directions are recommended: (1) Scalable manufacturing: Develop low-cost, scalable processes for embedding functional nanomaterials and responsive polymers into traditional textile substrates; (2) Multifunctional integration: Explore hybrid systems combining passive radiative cooling, active thermal regulation, and smart sensing to optimize comfort, durability, and energy performance; and (3) User-centric validation: Conduct extensive wearability, durability, and lifecycle studies under real-world conditions to ensure long-term performance, especially for vulnerable populations or harsh environments.

Overall, while thermoregulating textiles have reached a point of technical maturity in controlled settings, continued interdisciplinary innovation is essential to bring these materials into everyday use across diverse climates, occupations, and lifestyles.