Color tunable photo-thermochromic elastic fiber for flexible wearable heater

Flexible wearable heater plays a critical role in maintaining a consistent human body temperature, particularly during outdoor activities in cold environments, where garment elasticity, stretchability, and mechanical strength are paramount. Thus, there is an urgent demand for the development of flexible wearable heaters. In this study, we have successfully engineered a photo-thermochromic elastic fiber with control over its color properties via a continuous wet-spinning process. Through the incorporation of a modest amount (as little as 0.5%) of photothermally active polyaniline (PANI) and polydopamine (PDA) nanoparticles, this fiber exhibits exceptional photothermal conversion performance compared to pure thermoplastic polyurethane (TPU) fiber. Notably, when exposed to 600 W m⁻² irradiation for 600 s, the equilibrium temperature of the photo-thermochromic elastic fiber rises impressively from the ambient 20.0 °C to 53.5 °C. A significant feature of this fiber is its reversible color-changing capability, which can be conveniently controlled by manipulating the light source. This innovative characteristic empowers the user to monitor the fiber’s temperature by observing its color shifts. Furthermore, the fiber boasts exceptional stretchability, with an impressive elongation capacity of up to 500%, and remarkable resistance to washing, enduring up to 25 cycles. Taking this innovation further, we integrate the fiber into a fabric that maintains its superior photothermal conversion performance, mechanical resilience, and the ability to undergo reversible color changes when exposed to sunlight. This stretchable and vibrant photo-thermochromic elastic fiber holds significant promise as an energy-efficient alternative and is poised to find exciting applications in the realm of smart textiles.