Electrophoretically-Deposited Metal-Decorated CNT Nanoforests with High Thermal/Electric Conductivity and Wettability Tunable from Hydrophilic to Superhydrophobic

A single-step, room-temperature, and scalable electrophoretic deposition process is reported to form nanocomposites on any electrically conductive surface with metal nanoparticle decorated carbon nanotubes (CNTs). The contact angles (CAs) can be easily tuned from approximate to 60 degrees to 168 degrees by varying the deposition voltage, while hydrophobicity and superhydrophobicity surprisingly arise from the hydrophilic CNTs being deposited. The relatively high voltage tends to vertically align CNTs during deposition, leading to architectural micro/nanoscale roughness on the surface. The combination of the multiscale roughness along with the low surface energy of hydrocarbon functional groups on the CNT surface has enabled facile wettability control, including the Petal and Lotus effects. Further, the relatively vertical orientation of the CNTs, without any coating, allows for current and heat transfer along their axis with superior conductivity. Similar behavior in terms of CA control is seen for all three divalent metal ions in the deposition solution (i.e., Cu2+, Ni2+, and Zn2+) that are used to charge the CNTs while eventually getting co-deposited. This implies that this method could possibly be extended to other metals by selecting appropriate charging salt. A patterning technique is also demonstrated for facile fabrication of superhydrophobic CNT-metal islands surrounded by hydrophilic CNT coating.