Solar evaporation of liquid marbles with tunable nanowire array

Abstract

Solar interfacial evaporation is a potential and sustainable desalination technology. The structural design of photothermal materials plays an important role in improving the evaporation performance. Here, we propose a new evaporating structure consisting of liquid marble with tunable nanowire array to enhance solar evaporation. Such magnetically responsive nanowire arrays are enabled by controllable assembly of nanoparticles over the surface of liquid marble. Different from the traditional structure, the nanowire array increases light absorption through multiple reflection and to promote steam generation. Besides, the narrow space and local aggregation of particles within the nanowire array hinder heat diffusion to enhance evaporation efficiency. A series of experiments are conducted to validate the concept. The liquid marble with upward nanowire array (ULM) shows outstanding performance with the highest evaporation rate of 8.7 μg/s. This rate is 1.21, 1.04 and 1.04 times larger than that of liquid marble with nanoparticles (LM), left-tilt nanowire array (LLM) and right-tilt nanowire array (RLM). Numerical analysis further illustrates that the nanowire array concentrates the electromagnetic field and heat over the evaporative interface. The induced thermal-boundary layer with high-temperature thus improves the evaporation. This work provides a new concept of solar interfacial evaporation with tunable nanowire array, which has far-reaching implications in seawater desalination or wastewater treatment.