EAGER: Thermodynamic and structural behaviors of water evaporation assisted by superwicking surfaces

Providing clean water to people is essential and a great challenge. To help address this challenge, solar energy can be harnessed to purify wastewater or seawater by evaporation and condensation. A potentially efficient method for the evaporation step is to use solar-thermal interfacial evaporation, where solar heating and water evaporation occur together at the interface between air and water. However, interfacial evaporators are usually made of bulk porous materials that introduce many limitations. Recently, the team for this project developed a two-dimensional interfacial evaporator consisting of a metal surface containing microcapillaries. Enhanced wicking in the microcapillaries and efficient light absorbance in the metal produced highly efficient evaporation. This EAGER project will explore the mechanisms underlying the evaporator’s performance with the goal of producing optimal surfaces for high-efficiency interfacial water evaporation. The project will provide opportunities for undergraduates to participate in the research and will also sponsor open-house events for students to learn about technologies used in water research. Previous studies have shown that evaporation is strongly influenced by water clustering at the air-water and solid-water interfaces. To study the superwicking surface effects on water evaporation, two techniques will be applied - calorimetry and transient circular dichroism spectroscopy. The experiments will test the hypothesis that the highly efficient evaporation achieved in the two-dimensional evaporator is attributed to a reduction in the enthalpy of vaporization in the device’s microcapillaries. The outcomes will pave the way to design optimal surfaces for high-efficiency interfacial water evaporation and desalination, as well as to help understand other interfacial processes like corrosion, biofouling, bacterial growth, icing, boiling, and adsorption. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.