Bacterial Cellulose-Based Bilayer Passive Cooler for High-Performance Radiative/Evaporative Cooling

Passive cooling material presents a zero-energy solution to the rapidly increasing global demand for cooling. However, these materials face energy/resource-intensive and pollution-intensive manufacturing, posing significant challenges to scalability and long-term energy-saving applications. Here, biosynthesized bacterial cellulose (BC) with a 3D interconnect porous structure was employed as a versatile template to develop an BC-based bilayer passive cooler. The cooler consists of a methyltrimethoxysilane-modified hydrophobic BC (mBC) aerogel and a carboxymethyl cellulose-reinforced hydrophilic BC (cBC) adsorptive material named mBC@cBC. This forms an asymmetric interfacial structure with a hydrophobic radiative layer and a hydrophilic evaporative layer. Owing to the synergistic coupling of radiative and evaporative cooling, the mBC@cBC cooler achieves a sub-ambient temperature drop of 11.1°C on a clear day under 760 W·m −2 solar irradiation. Furthermore, it enables a remarkable temperature reduction exceeding 55°C on high-temperature surfaces (80°C). The cooler is broadly applicable to low-temperature storage, food preservation, and cold-chain logistics. This work addresses the challenges of low-carbon manufacturing and scalability in passive cooling materials and provides an innovative solution for sustainable and environmentally friendly cooling technologies.