Robust Superhydrophobic Carbon Nanotube Film with Lotus Leaf Mimetic Multiscale Hierarchical Structures

Abstract

Superhydrophobic carbon nanotube (CNT) films have demonstrated many fascinating performances in versatile applications, especially for those involving solid/liquid interfacial processes, because of their ability to affect the material/energy transfer at interfaces. Thus, developing superhydrophobic CNTs has attracted extensive research interests in the past decades, and it could be achieved either by surface coating of low-free energy materials or by constructing micro/nanohierarchical structures via various complicated processes. So far, developing a simple approach to fabricate stable superhydrophobic CNTs remains a challenge because the capillary force induced coalescence frequently happens when interacting with liquid. Herein, drawing inspirations from the lotus leaf, we proposed a simple one-step chemical vapor deposition approach with programmable controlled gas flow to directly fabricate a CNT film with rather stable superhydrophobicity, which can effectively prevent even small water droplets from permeating into the film. The robust superhydrophobicity was attributable to typical lotus-leaf-like micro/nanoscale hierarchical surface structures of the CNT film, where many microscale clusters composed of entangled nanotubes randomly protrude out of the under-layer aligned nanotubes. Consequently, dual-scale air pockets were trapped within each microscale CNT cluster and between, which could largely reduce the liquid/solid interface, leading to a Cassie state. Moreover, the superhydrophobicity of the CNT film showed excellent durability after long time exposure to air and even to corrosive liquids with a wide range of pH values. We envision that the approach developed is advantageous for versatile physicochemical interfacial processes, such as drag reduction, electrochemical catalysis, anti-icing, and biosensors.

Tuning the Wettability of Vertically Aligned CNT–TiO2 Hybrid Electrodes for Enhanced Supercapacitor Performance

“…Control of wettability and microstructure becomes a more challenging issue in micro supercapacitor where on chip integration of aligned CNTs is advantageous. Vertically aligned CNTs grown on Si/SiO 2 substrates are known to show remarkable superhydrophobicity with contact angle greater than 140° by trapping air pockets among CNT clusters leading to reduced liquid/solid interface . While the capillary forces tend to collapse the CNT forest structure to some extent, the reduced interaction of dense CNT forests with liquid limits the energy storage performance …”

Excellent oil/water separation performance of poly(styrene‐alt‐maleic anhydride)/fluorocarbon surfactant membrane filter with functionalized multiwalled carbon nanotubes

“…Jiang and coworkers prepared a densely packed CNT film with super‐amphiphobic properties (the contact angles for both water and oil are greater than 160°) and a honeycomb‐like aligned CNT film with superhydrophobic properties . Wang et al fabricated CNT films with lotus‐leaf‐like micro/nanoscale hierarchical surface structures, which exhibited rather stable superhydrophobicity . CNTs are also effective fillers to improve the properties of polymer matrices owing to their high elastic modulus, significant thermal resistance, and excellent adsorption capability .…”

Tunable Adhesion on Superhydrophobic Copper Surfaces Using a Facile Controllable Dewetting Approach

“…In principle, the adhesion property of a SHPB surface is mainly determined by the continuity of the three‐phase contact line (TCL), when it interacts with a liquid, which is highly dependent on the surface morphology. [ 8,9 ] Three typical SHPB contact states, including the Cassie state with low F ad , the Wenzel state with high F ad , and the transitional state with moderate F ad , normally regulate the dynamics of water droplets depending on the degree of penetration of a liquid into the textured surface. [ 9 ] As such, highly textured surfaces with a tunable topology and nonpolar chemical composition are necessary to realize tunable surface adhesion to SHPB surfaces.…”

“…[ 8,9 ] Three typical SHPB contact states, including the Cassie state with low F ad , the Wenzel state with high F ad , and the transitional state with moderate F ad , normally regulate the dynamics of water droplets depending on the degree of penetration of a liquid into the textured surface. [ 9 ] As such, highly textured surfaces with a tunable topology and nonpolar chemical composition are necessary to realize tunable surface adhesion to SHPB surfaces. So far, various surface adhesions have been observed on different SHPB surfaces using various strategies.…”