Polydopamine (Pdop) is coated on copper mesh (Cu mesh/Pdop). Upon heat treatment of the Cu mesh/Pdop, Pdop particles are newly formed at the surface of the Cu mesh/Pdop, which is used as a superhydrophilic mesh. After octadecylamine (ODA) is coated on the heat-treated Cu mesh/Pdop, hierarchical and strong ODA crystals are formed by special interactions between the ODA and the Pdop. The surface morphologies of the ODA crystals are tuned by varying the amount of Pdop particles. Similar results are obtained when the sponge is used as a template in lieu of the Cu mesh, and this sponge is used as a superhydrophobic sponge. A self-floating all-in-one device that simultaneously coexists in water as well as in oil is also prepared by combining the Pdop particle-mediated superhydrophilic mesh and superhydrophobic sponge composites. The self-floating all-in-one device simultaneously exhibits excellent removal performance for heavy metal ions in the water layer and excellent separation efficiency of oil in the oil layer due to its amphiprotic nature. (C) 2016 Elsevier Ltd. All rights reserved.