MXene-Decorated Smart Textiles with the Desired Mid-Infrared Emissivity for Passive Personal Thermal Management

Chameleon-inspired structural color fabrics with photoelectric dual-signal outputs for human motion monitoring

Structural color materials inspired by nature have garnered significant attention in textile dyeing and printing. However, most studies focus on eco-friendly fabric coloring, overlooking the functionality of structural colors. Designing intelligent structural color fabrics that integrate visual sensing and textile finishing technologies presents an ideal yet challenging research opportunity. Herein, a structural color fabric with photoelectric dual-signal outputs that mimics the skin of a chameleon is reported for smart wearable devices, and it is fabricated by integrating knitted fabric with conductive MXene materials and flexible photonic crystal films featuring a non-close-packed structure through thermal bonding, achieving visualized color variation and electrical signal outputs under mechanical strain. The prepared structural color fabric exhibits cyclic and sensitive changes in structural color (GFf = 2.07) and relative resistance (GFe = -1.45). It is worth mentioning that the MXene is introduced with two important functions: The primary function of the MXene pertains to the establishment of a conductive network, while the secondary function relates to the absorption of the scattered light produced by the photonic crystals. In addition, the black appearance of the conductive fabric is replaced by an adjustable structural color that serves the user's aesthetic needs for the product. This work provides novel insights into the development of functional structural color fabrics and demonstrates the great promise of non-close-packed photonic crystals structural color materials for smart wearable applications.

Terminal group engineering of Ti3C2Tx MXene on thermal emitter performance

Ti3C2Tx MXene has emerged as a promising material for diverse nanophotonics applications. In this study, we investigate how Ti3C2Tx MXene terminal groups (-F, -O-, -OH) influence the performance of a planar thermal emitter with a VO2/SiO2/Ti3C2Tx MXene structure. By examining four variants of Ti3C2Tx MXene across the 2-20 µm spectral range, we demonstrate that the hysteresis loop threshold temperature remains constant for all MXene types due to the VO2 phase change material. The average differential emissivity (Δε) between the semiconductor and metallic states of VO2 varies significantly with terminal group composition. The VO2/SiO2/Ti3C2F2 structure exhibits the highest differential emissivity of Δε = 0.42, while VO2/SiO2/Ti3C2(OH)2 shows the lowest of Δε = 0.33. The remaining structures; VO2/SiO2/Ti3C2 and VO2/SiO2/Ti3C2O2, demonstrate intermediate differential emissivity values of Δε = 0.41 and 0.38, respectively. These findings establish a foundation for controlling emissivity in applications such as energy harvesting, thermophotovoltaics, and radiative cooling systems. The ability to tailor thermal emission through MXene terminal group engineering presents opportunities for designing tunable photonic devices with precise thermal control capabilities for the next-generation of energy management systems.

Preparation and Thermal Properties of Magnetic PW@CaCO3@Fe3O4 Phase-Change Microcapsules and Their Application to Textile Fabrics

Multifunctional thermal regulation materials with good thermal properties, efficient magnetic performance, and satisfactory interface bonding on fabrics are highly desirable for protective fabrics, building winter protection materials, medical thermal regulation materials, and special-environment work clothing. Herein, a new class of magnetic phase-change PW@CaCO3@Fe3O4 microcapsules was successfully produced by controlling the content of magnetic Fe3O4 through a self-assembly method. The microstructure, chemical composition, phase-change behavior, and magnetic properties of the products were sequentially characterized and analyzed. The findings revealed that the obtained microcapsules possessed regular spherical structure with uniform size and excellent thermal properties. Furthermore, PW@CaCO3 with Fe3O4 (i.e., 8% mass fraction) showed the highest thermal regulation and magnetic properties and reached an enthalpy value of 94.25 J·g-1, which is clearly superior to the value of 77.51 J·g-1 for PW@CaCO3 microcapsules. At the same time, the encapsulation efficiency of 38.7% and saturation magnetization of 2.50 emu·g-1 were the best among the four given samples. Therefore, the good paramagnetic feature had a significant synergistic effect on the thermal properties of the PW@CaCO3 microcapsules under study. More importantly, multifunctional fabrics loaded with PW@CaCO3@Fe3O4 microcapsules still showed an enthalpy value of 25.81 J·g-1 after several washes and have the potential to be used widely in the field of temperature control. The thermal regulation fabrics in this study exhibited excellent thermal properties and fastness, which contribute to their practical applications in advancing multifunctional textiles and high-technology modern fabrics.

Adaptive fabric with emissivity regulation for thermal management of humans

The heat generation of the human body dramatically varies between resting and active status, so dynamic heat dissipation is required to ensure optimal thermal comfort. Herein, we propose a spectrally self-adaptive smart fabric (SSSF) by covering polyester fabric with silver nanowires, which autonomously adjusts its emissivity in response to the body's movement status from dry to wet states. During periods of inactivity, the SSSF maintains radiative heat insulation with a low emissivity state of 0.39. Conversely, during vigorous physical activity, its emissivity is improved to 0.83 when the sweat penetrates the SSSF, facilitating greater heat dissipation. Comparative experiments demonstrate the superior thermal management capabilities of the SSSF, with a 19.5 % reduction in heat dissipation power relative to traditional fabrics when in the low emissivity mode, and an impressive 67.6 % enhancement in heat dissipation power as it changes from low to high emissivity mode. This work provides an adaptive approach to emissivity modulation, offering an effective solution for dynamic heat dissipation of humans across various states of activity, thereby enhancing personal thermal comfort.

Solution-Processed Metallic Nanowire Network for Wearable Transparent Thermal Radiation Shield

Heating requirements for residential and commercial dwellings result in significant energy consumption and deleterious environmental effects. Personal radiative thermal management textiles regulate the wearer's body temperature by controlling the material's intrinsic optical properties. Passive heating textiles suppress radiative heat losses and therefore significantly reduce the energy consumption required for building heating systems. Guided by an optical theoretical approach, a transparent radiation shield (TRS) is designed based on silver nanowires (AgNWs) that can suppress human body heat with simultaneous visible light transmittance anticipated for practical fabrics. We experimentally demonstrated a TRS with large infrared light reflectance (low emissivity of 35%) and a visible (VIS) transparency value of 75% (400-800 nm). The results are well corroborated by the Mie scattering theory and the wire-mesh equivalent sheet impedance model, which provide fundamental mechanism understanding and guidance toward higher performance. The TRS is fabricated by a simple, solution-processing method with thermoplastic elastomer protective layers, granting notable stretching capabilities, mechanical robustness, and conformability to any body shape or object. The rigorous theoretical strategy enables the scalable synthesis of low-emissivity and visibly transparent textiles for personal thermal comfort.

High Thermal Conductivity and Radiative Cooling Designed Boron Nitride Nanosheets/Silk Fibroin Films for Personal Thermal Management

The implementation of passive cooling strategies is crucial for transitioning from the current high-power- and energy-intensive thermal management practices to more environmentally friendly and carbon-neutral alternatives. Among the various approaches, developing thermal management materials with high thermal conductivity and emissivity for effective cooling of personal and wearable devices in both indoor and outdoor settings poses significant challenges. In this study, we successfully fabricated a cooling patch by combining biodegradable silk fibroin with boron nitride nanosheets. This patch exhibits consistent heat dissipation capabilities under different ambient conditions. Leveraging its excellent radiative cooling efficiency (Rsolar = 0.89 and εLWIR = 0.84) and high thermal conductivity (in-plane 27.58 W m-1 K-1 and out-plane 1.77 W m-1 K-1), the cooling patch achieves significant simulated skin temperature reductions of approximately 2.5 and 8.2 °C in outdoor and indoor conditions, respectively. Furthermore, the film demonstrates excellent biosafety and can be recycled and reused for at least three months. This innovative BNNS/SF film holds great potential for advancing the field of personal thermal management materials.

Stepless IR Chromism in Ti3 C2 Tx MXene Tuned by Interlayer Water Molecules

Real-time control over infrared (IR) radiation of objects is highly desired in a variety of areas such as personal thermal regulation and IR camouflage. This requires the dynamic modulation of IR emissivity in a stepless manner over a wide range (>50%), which remains a daunting challenge. Here, an emissivity modulation phenomenon is reported in stacked 2D Ti3 C2 Tx MXene nanosheets, from 12% to 68% as the intercalation/discharging of water molecules within the interlayers. The intercalation of water molecules dynamically changes the electronic properties and the complex permittivity in IR frequencies of Ti3 C2 Tx . This emissivity modulation is a stepless and reversible process without the assistance of any external energy input. Further, intercalating cellulose nanofibers into the Ti3 C2 Tx interlayers makes this dynamic process highly repeatable. Last, a sweat-responsive adaptive textile that can improve thermal comfort of human body under changes in metabolic rates and environmental conditions is demonstrated, showing great potential of this mechanism in passive on-demand radiation modulation.

A Hierarchically Nanofibrous Self-Cleaning Textile for Efficient Personal Thermal Management in Severe Hot and Cold Environments

Climate change has recently caused more and more severe temperatures, inducing a growing demand for personal thermal management at outdoors. However, designing textiles that can achieve personal thermoregulation without energy consumption in severely hot and cold environments remains a huge challenge. Herein, a hierarchically nanofibrous (HNF) textile with improved thermal insulation and radiative thermal management functions is fabricated for efficient personal thermal management in severe temperatures. The textile consists of a radiative cooling layer, an intermediate thermal insulation layer, and a radiative heating layer, wherein the porous lignocellulose aerogel membrane (LCAM) as intermediate layer has low thermal conductivity (0.0366 W·m-1·K-1), ensuring less heat loss in cold weather and blocking external heat in hot weather. The introduction of polydimethylsiloxane (PDMS) increases the thermal emissivity (90.4%) of the radiative cooling layer in the atmospheric window and also endows it with a perfect self-cleaning performance. Solar absorptivity (80.1%) of the radiative heating layer is dramatically increased by adding only 0.05 wt% of carbon nanotubes (CNTs) into polyacrylonitrile. An outdoor test demonstrates that the HNF textile can achieve a temperature drop of 7.2 °C compared with white cotton in a hot environment and can be as high as 12.2 °C warmer than black cotton in a cold environment. In addition, the HNF textile possesses excellent moisture permeability, breathability, and directional perspiration performances, making it promising for personal thermal management in severely hot and cold environments.