Abstract:

Objective Existing temperature-regulating textiles are known for not meeting thermal regulation requirement under specific climates, impairing thermal comfort. Thermosensitive textiles show large variations in thermal sensing ranges, with complex manufacturing and poor washability. Furthermore, humidity-sensitive textiles also fail to adjust thermal regulation with temperature. Herein, structure-driven wet-responsive textiles were prepared via core-sheath yarn actuators based on the multi-level helical structure design and the resulting chiral loops of the fabrics. Combined with boron nitride (BN) and γ-(methacryloyloxy)propyl trimethoxysilane (KH-570) hydrophobic finishing and poly(2-(methacryloyloxy)ethyl)dimethyl-(3-sulfopropyl)ammonium hydroxide(PDMAPS)grafting, a thermosensitive amphiphilic interface was constructed, realizing synergistic humidity-temperature dual-response regulation.

Method Viscose and polyester yarns with optimal twist(the twist of viscose yarn at 1 200 per meter, and polyester yarns at 500 per meter) were heat-set at 90 ℃ and 200 ℃. Core-sheath yarn actuators were prepared using viscose as covering yarn and polyester as core yarn (winding density at 50 per centimeter). These yarns were knitted into a plain knitted fabric, then the fabric was stretched and heated to form the chiral looped structure. The as-prepared fabrics were then soaked in BN/KH-570 solution, dried, then immersed in DMAPS/phosphate buffer (1∶10 mass ratio, 1∶40 liquid-fabric ratio) with horseradish peroxidase (HRP), acetylacetone (ACAC), H₂O₂. Reaction ran at 37 ℃ in nitrogen oil bath. Fabrics were washed in deionized water and then air-dried to obtain the treated fabric sample PDMAPS-BN/KH-570. Core-sheath yarn actuator driving performance and fabric's temperature-humidity response were studied.

Results A comparison was made between the core-sheath polyester/viscose yarn and heat-set viscose yarn. The research unveiled a series of significant differences. When it came to torsional actuation and recovery, the core-sheath polyester/viscose yarn showed low hysteresis, indicating low energy loss and speedy recovery. The core-sheath yarn structure was remarkably stable and durable, ensuring long-term performance without degradation. In terms of mechanical strength, core-sheath polyester/viscose yarn outperformed the heat-set viscose yarn by a large margin in that the breaking strength of the former was 3.4 times that of the latter, indicating superior ability to withstand tension without breaking. The breaking elongation of the former was 1.25 times higher than that of the latter, showing better flexibility and stretchability. Focusing on the fabric made from the core-sheath polyester/viscose yarn, it was of interest to note that when fully wet, the porosity of the fabric increased from 12.75% in the dry state to 25.25%, nearly doubling. Moreover, it could smoothly switch between dry and wet states within this porosity range, providing great adaptability to personal microenvironment. The response temperature played a crucial role in regulating the fabric surface property. At 25 ℃, the water contact angle of the fabric was about 107°, and water droplets stayed on its surface for over 20 s, demonstrating clear hydrophobicity. However, when the temperature rose to 40 ℃, the water contact angle rapidly decreased to 0 within 12 s, and the fabric turned hydrophilic. This reversible change between hydrophilic and hydrophobic states enabled adaptive regulation of heat convection, conduction, and radiation. In practical applications, when the fabric was wetted at high temperatures, the cuff size of a sleeve made from the core-sheath polyester/viscose yarn increased by 9.01%, and the sleeve length shrank by 6.51% due to the torsional deformation of chiral loops of the knitted fabric. In contrast, when exposed to moisture at low temperatures, it remained unchanged in shape, showing excellent stability. Furthermore, the fabric excelled in various aspects compared to commercial fabrics, such as softness, flatness, resilience, and drape. All these properties make the fabric a promising material for a wide range of uses.

Conclusion Through the design of textile multi-level structure, a knitted fabric with intelligent humidity and temperature self-adaptive intelligent temperature regulation function is developed, using the prepared viscose/polyester wrapped yarn. Then the temperature responsive polymer was introduced through a two-step grafting process to achieve the adaptive control of the fabric on the characteristics of heat convection, heat conduction and heat radiation. Besides, the response temperature of the textile is controlled at about 35 ℃, and its porosity can achieve dynamic switching from 12.75% to 25.25% between the dry and wet state. The tight knitted structure with low porosity in dry state facilitates body heat retention in cool environments. Upon wetting, the porosity increases to enhance thermal and moisture transfer to accelerate evaporative cooling during perspiration. When this fabric is made into sleeves, it undergoes adaptive structural and dimensional changes in scenarios where the human body sweats at high temperatures. These adaptive changes can regulate temperature, enabling the human body to maintain a comfortable sensory experience. This fully demonstrates its potential for manufacturing smart clothing and provides a new path to enhance the stability, robustness and personalized control ability of smart textiles in changing environments. In addition, the uniform wet response law was also observed in the knitted fabrics with the same structure made of cotton and nylon, which confirmed that the textile multi-level structure design strategy had good versatility.

Key words: smart textile, artificial muscle, wrapped yarn, structure-driven, temperature-sensitive polymer, humidity-temperature dual-response fabric, thermal management textiles