Asymmetric Janus Fibers with Bistable Thermochromic and Efficient Solar–Thermal Properties for Personal Thermal Management

The compelling combination of thermochromism and multifunctional wearable heaters in smart textiles has received increasing attention given the significant synergistic effect of green solar heat supply and energy storage. However, due to color incompatibility and poor knittability, developing fabrics with bistable thermochromic properties to achieve efficient solar–thermal management remains a challenging endeavor. Here, by combining bistable thermochromic, photochromic, and efficient solar–thermal properties, we constructed an asymmetric Janus (Janus A/B) fiber (BTCSJF) that can simultaneously display two colors and help with energy reserve while harvesting solar power. Benefiting greatly from donor–acceptor electron transfer, dynamic hydrogen bonding, and supercooling properties, BTCSJF displays a quick switch in color, excellent bistability, and enhanced performance in storing phase-change energy. In addition, BTCSJF can be self-heated by 35.6 °C higher than conventional fibers because it can capture and store solar energy. This research outlines a method to fabricate braided fibers with two theoretically incompatible properties that have promising implications for self-powered integrated bistable color-changing and personal thermal management applications. Graphical Abstract An asymmetric Janus light absorbent/bistable thermochromic fiber (BTCSJF) was designed and fabricated, which can combine solar energy, phase-change energy storage, and bistable thermo- and photochromic properties. The unique Janus structure allows it to be used as a portable heater to stimulate color changes without obscuring color due to dark photothermal materials. Meanwhile, the heat energy converted by solar energy can be stored for personal thermal management.