A tree-root mimicked Janus evaporator for solar evaporation of saturated saline water

Solar water evaporation is attracting tremendous attention due to its promising applications in seawater desalination, clean water production and purification with high efficiency and zero carbon emission. However, salt crystallization on evaporators drastically decreases the evaporation rate of seawater. Herein, we demonstrate a new type of bionic solar evaporation system with microchannels and macrochannels possessing different wettabilities working as Janus devices inspired by the functions of poplar trees. Salty water can be transported to the surface of the evaporator via microchannels by capillary force, and the water diffuses on the top of the tree-root mimicked evaporator. The remaining water after evaporation flows back to bulk water through macrochannels before the crystallization of salt, leading to the excellent salt rejection performance of our evaporation system. The evaporation rate of our bionic evaporator can reach 1.123 kg m-2 h-1 for high-concentration saline water. Moreover, the long-term desalination performance of our evaporation system has been well achieved with a purification rate of metal ions as high as 99.9%. Most significantly, a suitable arrangement of microchannels and macrochannels is optimized to achieve saturated saline water desalination with a high evaporation rate, demonstrating the effective and stable performance of our bionic evaporation system for extremely high-concentration saline water desalination. We demonstrate a new type of solar evaporation system with microchannels and macrochannels possessing different wettabilities working as Janus devices inspired by poplar trees, leading to effective water evaporation and salt rejection performance for saturated saline water.