3D-Printed Hemispherical Capillaries for Solar Water Evaporation

Solar interfacial evaporation offers a sustainable method to extract fresh water from seawater, but is often constrained by salt accumulation. A 3D-printed hemispherical solar evaporator with integrated open capillary grooves on its surface is introduced to enhance water transport and evaporation. This design creates a vertically nonuniform liquid film, initiating Marangoni flow to facilitate continuous desalination. The evaporator achieves high evaporation rates of 2.768 kg m⁻² h⁻¹ for pure water and 2.646 kg m⁻² h⁻¹ for 25 wt% saline water upon one-sun solar irradiation. This high performance is attributed to the microporous structure of the capillaries, which supports cluster-based water evaporation and benefits from the lower evaporation enthalpy of seawater. After 15 h of operation, the hemispherical capillary design promotes localized salt crystallization at low concentrations and forms a thin salt film at higher concentrations, surprisingly increasing the evaporation rate. Moreover, the structure effectively removes pollutants, including heavy metals and organic contaminants from wastewater and seawater. This new evaporator could significantly impact wastewater treatment, desalination, and other evaporative applications.