Sweat-Driven Silk-yarn Switches Enabled by Highly Aligned Gaps for Air-conditioning Textiles

Smart textiles are attracting great interest. Particularly, air-conditioning textiles are highly desired for their merits in energy conservation and personal temperature/humidity management. Currently, air-conditioning textiles can be fabricated by two strategies. One uses infrared-radiation-adaptive materials, and the other uses moisture-responsive actuators that can regulate temperature and humidity simultaneously. Here, the fabrication of a silk-yarn switch comprising electrospun highly aligned nanofibers is reported and its application in air-conditioning textiles is demonstrated. Silk yarn rotates in contact with liquid, and can be recovered by drying. The different responses and wetting behaviors of the switch to H2O and C2H6O is investigated. It is argued that alignment and surface hydrophilicity of nanofibers play important roles in this term. To elaborate, actuating trait is mainly controlled by reduction of the surface free energy of aligned silk nanofibers, during the wetting process. As proof of concept, the application of the sweat-driven silk-yarn switch in regulating the temperature/humidity of the human body is demonstrated in this work. Considering the large production, versatile processibility, and good biocompatibility, silk actuator may have practical applications in designing smart switches (or valves) for intelligent textiles, artificial muscles, and other application scenarios.