It is not easy for water droplets to slide on the CNTs/Si surface due to large SA. Some water droplets sprayed into CNTs/Si disperse into the cavities of the CNT forest, making the wetting surface of the CNTs and some tiny water droplets gather into large drops. The large water droplets on the CNTs/Si surface deform into irregular shapes due to wetting, which are quite different from those on the CNTs/Si-μp. The water droplets we observed on the CNTs/Si surface have a diameter above 5 mm (approximately 52 μL). In our

experiments, the CNT forest, no matter growing on planar Si wafer or Si micropillars, might absorb tiny water droplets. The CNTs/Si-μp still have superhydrophobic properties after adsorbing water and drying. In contrast, the CNTs/Si lose their superhydrophobic properties. Figure  4 shows SEM images of the Pitavastatin order CNT forest after wetting using tiny water droplets. It is clear that the CNT Ruboxistaurin nmr forest shrinks driven by capillarity force after wetting, but the CNTs still suspend among the Si micropillars (Figure  4a,b). Although the air cavities within CNTs might reduce significantly, the air cavities between Si micropillars are maintained. The CNTs/Si-μp still have a hierarchical structure after drying and thus show hydrophobic properties. For the CNTs growing on planar Si wafer, vertical-standing CNTs were destroyed and form a cellular structure on Si wafer (Figure  4c,d), which

is similar to a recent report [19]. The air cavities within CNTs are eliminated, so the CNT forest on planar Si wafer loses its superhydrophobic properties. Figure 4 SEM images of CNTs/Si-μp and CNTs/Si after wetting. (a) Low- and (b) high-magnification SEM images of CNTs/Si-μp after wetting using nebulizer droplets. (c) Low- and (d) high-magnification SEM images of CNTs/Si after wetting using nebulizer droplets. Conclusions In summary, the hierarchical architecture of CNTs/Si-μp has a superhydrophobic surface with large CA and ultralow SA of only 3° to 5°. Tiny water droplets larger than 0.3 μL can slide on CNTs/Si-μp with a tilted angle of 5°, showing a high capacity of collecting water droplets. After wetting using tiny water

droplets, the CNT forest growing on planar Si wafer loses its superhydrophobic properties, but the CNTs/Si-μp still have a superhydrophobic surface because Alanine-glyoxylate transaminase they still have a hierarchical structure. The CNTs/Si-μp show stable superhydrophobic properties. Acknowledgements This work is financially supported by the National Natural Science Foundation of China (51172122, 11272176), Foundation for the Author of National Excellent Doctoral Dissertation (2007B37), Program for New Century Excellent Talents in University, and Tsinghua University Initiative Scientific Research Program (20111080939). References 1. Luo MX, Gupta R, Frechette J: Modulating contact angle hysteresis to direct fluid droplets along a homogenous surface. ACS Appl Mater Interfaces 2012, 4:890.CrossRef 2. Wang ST, Jiang L: Definition of superhydrophobic find more states.