Graphene-coated meshes for electroactive flow control devices utilizing two antagonistic functions of repellency and permeability

Abstract

The wettability of graphene on various substrates has been intensively investigated for practical applications including surgical and medical tools, textiles, water harvesting, self-cleaning, oil spill removal and microfluidic devices. However, most previous studies have been limited to investigating the intrinsic and passive wettability of graphene and graphene hybrid composites. Here, we report the electrowetting of graphene-coated metal meshes for use as electroactive flow control devices, utilizing two antagonistic functions, hydrophobic repellency versus liquid permeability. Graphene coating was able to prevent the thermal oxidation and corrosion problems that plague unprotected metal meshes, while also maintaining its hydrophobicity. The shapes of liquid droplets and the degree of water penetration through the graphene-coated meshes were controlled by electrical stimuli based on the functional control of hydrophobic repellency and liquid permeability. Furthermore, using the graphene-coated metal meshes, we developed two active flow devices demonstrating the dynamic locomotion of water droplets and electroactive flow switching.

Functionally Antagonistic Hybrid Electrode with Hollow Tubular Graphene Mesh and Nitrogen‐Doped Crumpled Graphene for High‐Performance Ionic Soft Actuators

“…Ni or Cu mesh can be cut into any shape and size and applied as a catalytic substrate for CVD to achieve a GM with the desired shape . By etching the metallic skeleton, hollow tubes of graphene can be obtained and it can form a macroscale mesh‐type architecture woven with each other . Most importantly, the wavy pattern of the hollow tubular mesh structures renders them much more stretchable than other types of graphene architecture such as graphene paper.…”

“…To obtain a free‐standing GM, the Ni was removed by soaking the samples in hot (80 °C) HCl solution (3 m ) for 24 h. By dissolving the Ni, the hollow graphene meshes floated to the top of the solution. The samples were washed with DI water and dried by freeze‐drying …”

“…First, a suitable solvent must be selected for the electrode dispersion. Since GM is hydrophobic, it does not submerge in a water‐based dispersion and instead floats on the surface . It prevents the electrode material from penetrating into the mesh holes and forming a monolithic electrode.…”

External‐Field‐Induced Gradient Wetting for Controllable Liquid Transport: From Movement on the Surface to Penetration into the Surface

“…Tabassian et al reported electric-field-induced wetting of nickel meshes coated by graphene for use as flow control devices (Figure 9). [137] The droplet shapes and water penetration through the meshes can be controlled by an electric field. Based on electric-fieldinduced wetting, the CA of the conductive liquid (e.g., water) Figure 9.…”

“…Reproduced with permission. [137] Copyright 2016, Nature Publishing Group. can be effectively reduced, while it has almost no effect on a nonconductive oil droplet in air, and the oil CA even increases in water.…”