Thermal Rectification in Gradient Microfiber Textiles Enabling Noncontact and Contact Dual-Mode Radiative Cooling

Abstract

Radiative cooling textiles characterized by high solar scattering and significant mid-infrared emission properties present a promising energy-efficient solution for cooling objects exposed to high temperature and direct sunlight conditions. However, the inherent porous structure and thermal insulating properties of textiles pose challenges in effectively cooling self-heated objects. Herein, the fabrication of an ultra-flexible is presented, gradient-structured microfiber composite textile using a filtration-induced entrapment and hot-pressing method. This textile features a unique concentration gradient of thermally conductive boron nitride nanosheets across its thickness, leading to a gradient distribution of stacking pore sizes. This gradient configuration induces multiple Mie scattering across the entire spectrum of incident sunlight, thereby achieving an impressive solar reflectance of up to 97.3%. Moreover, this textile demonstrates a thermal rectification factor of 31.8%, enabling efficient dual-mode radiative cooling capabilities in both noncontact and contact scenarios. In noncontact cooling scenarios, this textile effectively reduces the temperatures of unheated and self-heated enclosed spaces by 9.2 and 8.7 °C, respectively, outperforming typical textiles. Additionally, this textile shows enhanced radiative cooling capabilities in contact cooling scenarios, lowering the temperature of underlying self-heated objects by 8.6 °C compared to typical textiles.