Abstract:

Significance With the intensification of global warming and the increasing frequency of extreme high-temperature weather, human body is more susceptible to overheating in hot and humid environments, posing significant risks to health, comfort, and productivity. Moisture-responsive textiles, as an emerging class of smart materials, can autonomously sense humidity changes and adapt their structural configurations to optimize personal thermal and moisture management. Compared with woven fabrics, knitted fabrics feature loop-based structures that are inherently flexible, deformable, and permeable, making them particularly suitable for moisture-triggered actuation. Upon exposure to moisture, fiber swelling or deswelling induces reversible loop deformation, enabling dynamic control over fabric porosity and heat dissipation. Therefore, the development of moisture-responsive knitted fabrics holds substantial promise for advancing next-generation intelligent clothing systems that enhance wearer comfort while reducing energy consumption for cooling. This review systematically examines recent progress in this field, emphasizing design strategies across multiple scales and identifying key challenges and future directions for practical implementation.

Progress Recent advances in moisture-responsive knitted fabrics were summarized across fiber, yarn, and fabric scales. At the fiber level, two main strategies are employed, i.e. modifying natural fibers and engineering bicomponent fibers. Chlorination of wool removes scale layers, enabling reversible crimp extension upon wetting, which enhances fabric porosity and reduces surface temperature compared to the dry state. Bicomponent fibers with asymmetric hydrophilicity-hydrophobicity components, such as triacetate-diacetate fibers and polyester-based asymmetric peanut-structured fibers, bend toward the hydrophobic side under humidity due to differential swelling, thereby enlarging fabric pores and improving permeability. At the yarn level, helical structures are fabricated from twisted cellulosic fibers. Double-helix yarns, obtained by self-balancing twisted fiber assemblies, generate reversible torsional actuation that can roll up fabric sleeves during sweating. Single-helix actuators with twist-stable configurations untwist and lengthen in wet states, increasing loop size and fabric porosity for enhanced evaporative cooling. At the fabric level, asymmetric loop arrangements induce directional contraction upon wetting, reducing skin coverage and improving air permeability. Bioinspired artificial pores are created by patterning hydrophilic hydrogels on hydrophobic knitted substrates, and the hydrogel swells upon moisture absorption, opening predefined slits to regulate evaporative cooling. Covalent crosslinking strategies have been developed to enhance the cyclic stability of such moisture-responsive actuators. These multi-scale strategies collectively optimize moisture management through coordinated fiber deformation, yarn actuation, and fabric architecture design.

Conclusion and Prospect Although moisture-responsive knitted fabrics have demonstrated considerable potential in laboratory settings, several barriers must be addressed to enable their transition to practical applications. Firstly, the absence of standardized evaluation protocols hinders cross-study comparisons and obscures critical performance attributes such as tactile comfort, durability, and wearability under realistic conditions. Future work should prioritize the development of comprehensive testing frameworks that incorporate human subject trials across varying sweat rates, environmental conditions, and activity levels. Secondly, the reliance on specialized materials and multistep fabrication processes such as double-helix yarns limits scalability and increases production costs. Simplifying manufacturing routes while preserving responsiveness is essential for industrial adoption. Finally, long-term durability, particularly resistance to repeated laundering and mechanical stress, remains underexplored. Systematic assessments of washing stability and material fatigue are urgently needed. In the futural research, integrating sustainable bio-based fibers, tailoring fabric responses to different sweating intensities, and advancing scalable finishing technologies will be critical. With continued innovation, moisture-responsive knitted fabrics can evolve into affordable, eco-friendly, and durable smart textiles suitable for mass production and everyday personal thermal management.

Key words: moisture-responsive knitted fabric, personal thermal management, thermal and moisture comfort, hydrophilic/hydrophobic structure design, fiber swelling