A bio-inspired, hierarchically porous structure with a decoupled fluidic transportation and evaporative pathway toward high-performance evaporation

Abstract

Reeds are fast-growing plants continuously transporting and evaporating water from roots through the stem and leaves into the environment. Inspired by this naturally occurring process, we developed a high-performance evaporator with a decoupling fluidic transport and evaporation pathway by engineering the natural reed's structure via chemical delignification. The lignin removal enlarges the diameter of reed's multiscale channels and opens more pits and nanopores connecting these aligned channels. With this modified hierarchically porous structure, fast fluidic transport occurs mainly through the microscale channels and nanochannels based on the capillary effect, while the interconnecting pits and nanopores enable lateral transport into the macroscale channels, where their high surface area promotes efficient evaporation. As a consequence, the delignified reed demonstrates a high fluidic transport velocity of 14.7 mm s⁻¹ and evaporation rate of 46.9 kg m⁻² h⁻¹, which are 160- and 7-times faster than those of natural reeds, and much higher than those of delignified wood and commercial polyester. This evaporator design based on a delignified reed structure can be potentially employed for a large range of applications, such as evaporating ethanol or sterilant for killing airborne bacteria and viruses, evaporating water for adjusting indoor humidity and temperature, even producing clean water, and harvesting evaporation-driven energy.