Engineering biomimetic cellulose fabric for sustainably and durably cooling human body

It is essential and challenging to develop sustainable and durable passive radiative cooling materials for long-term effectively maintaining human thermal comfort when undergoing intensified global warming in our low-carbon society. Herein, inspired by the distinct structure-property relationship of fruits-branches in fruiter, this work designs an approach of fibrillation of cellulosic fibers (branches of fruiter) followed by in-situ synthesis of SiO2 nanoparticles (fruits of fruiter) easily to prepare sustainable, robust, customizable, and scalable cooling cellulose fabric. Such coupling strategy of cellulosic-fiber fibrillation and SiO2 in-situ growth strongly roughens cellulose fabric, more specifically, sufficient micro- and nano-sized cellulose fibrils and SiO2 particles, which enables our cooling cellulose fabric to effectively reflect solar light with 97% reflectance (0.4–1.0 µm) and emit mid-infrared light with 0.97 emissivity (8–13 µm). As a result, the developed cooing cellulose fabric spontaneously cools the human body with a temperature drop of 7.4 °C in high-temperature summer. It should be noted that the developed strategy realizes extraordinary adhesion performance between nanosized SiO2 and fibrillated cellulosic fibers, endowing cooling cellulose fabric with durable yet effective cooling distinction despite enduring 100-time mechanical washing and 100-day exposure to air, as well as high strength (∼48 MPa), desirable moisture evaporation rate and breathability. The present work demonstrates a promising strategy how durability, functionality, and customizability can be integrated in future material design.