A smart underoil“water diode”Janus TiO2 mesh membrane

Recently, Janus membranes with particular ability in unidirectional water permeation, known as “water diode”, have attracted increased attention. However, almost all existing Janus membranes are focused on controlling water permeation in air, similar membranes can work in complicated environments, such as oil, are still quite unusual, let alone with smart controllability. Herein, we report a TiO2 nanostructures coated mesh membrane. The membrane’s surface wettability can be reversibly switched between uniformly underoil superhydrophobicity and Janus underoil hydrophobicity/hydrophilicity as unilateral UV irradiation and heating are alternately carried out, consequently, on/off control of water permeation between blocking state and unidirectional penetrating state can be realized. Moreover, by controlling the size of the region irradiated by UV light for 50 min, penetrating channels with controlled size can be designed. Based on this advantage, different independent penetrating channels with diameter from 2 mm to 10 mm can be obtained, and precise control of water permeation flux from 48,432 Lm−2h−1 to 70,553 Lm−2h−1 can be achieved. Finally, based on the excellent controllability, some significant applications such as the removal of water from oil, underoil multichannel chemical reaction, and droplet pumping were also demonstrated. This work reports a new membrane with smart underoil water permeation controllability, given its controllability and particular wetting performance, it is potentially used in many fields, for example, oil purification, droplet manipulation, and microfluidic devices.