Controllable water permeation on a poly(N-isopropylacrylamide)-modified nanostructured copper mesh film.

Water permeation is important for various applications in industry, agriculture, and daily life. However, most research mainly focuses on the static wettability on different surfaces, and the dynamic properties of the micro- and nanostructure-enhanced responsive wettability is lacking. And the relevant application research is rare, which still remains a challenge. Herein we report the temperature-controllable water permeation on a poly(N-isopropylacrylamide)-modified nanostructured copper mesh film. At low temperatures (below 25 degrees C), the film shows good water permeability because of the highly hydrophilic nature, and as a result, the water can easily penetrate through the film. At high temperatures (above 40 degrees C), it is impermeable to water because of the superhydrophobicity and the large negative capillary effect induced by the micro- and nanostructures. The excellent controllability of water permeation on this film may be convenient for use in many processes including filtration, water/oil separation, and so on. A detailed investigation indicates that the special nanostructures and the appropriate size of the microscale mesh pores not only influence the static contact angles of the mesh film, but also, more importantly, greatly improve the dynamic properties of wettability at different temperatures simultaneously, which plays a crucial role in the excellent controllability over water permeation on this film. This work may also provide interesting insight into the design of novel functional devices that are relevant to surface wettability.