Designing lotus-like superhydrophobic self-cleaning surface using carbon nanotubes

Artificial superhydrophobic and self-cleaning surfaces are desirable in many engineering applications. Lotus leaves have long been the benchmark for the design and fabrication of artificial non-wetting surfaces. Here, we report the design and fabrication of superhydrophobic surfaces that mimic the behavior of lotus leaves. Akin to the microstructure of lotus leaves, an intrinsically hierarchical microstructure is created using carbon nanotubes (CNTs). The conventional CNT growth protocol is modified to induce multiscale features with lower diameter CNTs on the top of thicker CNTs. Together they form a dandelion seed head type structure with thicker CNTs such as “beak” and thinner CNTs such as “pappus.” The wetting and self-cleaning behavior of the CNT coated surface is compared with the lotus leaves. The wetting behavior of never-wet commercial spray and Cu and Ni foils are also recorded for comparison. The contact angle, contact angle hysteresis, and sliding angle of water drops on CNT coated surface are comparable with the lotus leaves. The wobbling motion of water drops on the CNT coated surface is similar to that on the lotus leaves and spray coated surface with varying contact line length with time. It also induces the self-cleaning characteristics of CNT coated surfaces similar to lotus leaves. Finally, the present study demonstrates a feasible strategy to design and fabricate lotus leaves like artificial superhydrophobic surfaces with hierarchical CNT structures.