Controllable Water Penetration through a Smart Brass Mesh Modified by Mercaptobenzoic Acid and Naphthalenethiol

In this paper, a novel pH-responsive brass mesh modified by 3-mercaptobenzoic acid (MBA) and 2-naphthalenethiol (NPT) was demonstrated via a facile chemical etching method followed by surface modification. The smart wettability was dependent on the assembled MBA and NPT with suitable thiol proportions. The on–off control of water penetrating intelligently into the nanostructured brass mesh substrate was carried out by the pH change in the outside environment. The brass mesh modified with XNPT = 0.4 (mole fraction of NBT in the mixed solution) exhibited the strongest pH responsivity from superhydrophobicity to superhydrophilicity. Furthermore, the resulted Janus membrane (JM) fabricated by the integration of a smart brass mesh and hydrophobic Ni foam could be used as a water diode in air and liquid systems. Unidirectional penetration for the water droplet was realized by the resulting smart JM with a hydrophobic upper layer and a pH-responsive layer below.