Directional and Continuous Transport of Gas Bubbles on Superaerophilic Geometry‐Gradient Surfaces in Aqueous Environments

Abstract

Due to the direct and sufficient contacting with the aqueous environment, the directional and continuous transport of gas bubbles on open surface without energy input will advance a variety of applications in heat transfer, selective aeration, water electrolysis, etc. Unfortunately, the behaviors of gas bubbles in aqueous environment are mainly dominated by the buoyancy moving gas bubbles upward, resulting in their difficult manipulation. Therefore, realizing the directional and continuous transport of gas bubbles on open surface still remains a great challenge. Herein, a novel strategy integrating the superaerophilic wettability with geometry‐gradient structure is proposed, which can engender high driving force and low hysteresis resistance force acting on the gas bubbles. In experiment, these fabricated superaerophilic geometry‐gradient polyethylene surfaces demonstrate distinguished performance of directionally and continuously transporting gas bubbles on open surfaces without energy input. In addition, the antibuoyancy bubble transportation device and the underwater bubble microreactor are successfully prepared in this manuscript, both of which illustrate the feasibility in the applications of complex environment and gas‐related fields. It can be envisioned that this study will promote the understanding and development of underwater functional superwettability materials to achieve the directional and continuous transport of gas bubbles on the open surface.

Anisotropic Spreading of Bubbles on Superaerophilic Straight Trajectories beneath a Slide in Water

“…The surface tension and later buoyancy are two crucial factors to drive the rapid evolution of bubbles spreading in three typical stages and further confirmed that the characteristic spreading time (10 ms) of the bubble on a superaerophilic surface (SALS) is much shorter than that in other plates, which agrees well with the results of Wang et al [18]. Moreover, Ma et al [19] combined the geometry-gradient structure with the spreading of bubbles on the upper SALS to manipulate the directional transport of bubbles without energy input.…”

“…This migration capacity of the ruptured bubbles provides a potential solution for the horizontally directional transport of the bubble in aqueous environments. Ma et al recently proposed this interesting topic [19], using the geometry gradient of the SALS to transport the bubble horizontally. Once the two sub-bubble humps established as a result of the interface necking before rupture, a high degree of symmetry in the two ruptured bubbles, including the migration velocity and bubble geometry, can be found during this whole dynamical process ( Figures 5 and 7).…”

“…As discussed above, previous research has been devoted to studying the dynamics of bubbles collision with surfaces [14], the directional and continuous transport of bubbles on superhydrophobic plates [19], or isotropic spreading on SALSs [15]; however, to our knowledge, no results aimed at the anisotropic spreading of bubbles on the SALSs have yet been reported. The anisotropic spreading of bubbles on the designated superaerophilic areas may motivate the novel technologies to enhance or reduce the reaction rate, mass, and heat transfer rate in some specific positions and then to improve the equipment performances in mineral flotation, selective aeration, bubble reactors, and so on.…”

An Innovative Design by Single‐Layer Superaerophobic Mesh: Continuous Underwater Bubble Antibuoyancy Collection and Transportation

“…To date, numerous efforts have concentrated on directional manipulation of underwater bubbles. To achieve gradient wettability at the surface of materials, many researchers have developed a series of gradient geometries, such as ratchets, cones, trapezia, and cylinders, and gradient surface free energy, for underwater gas bubbles transport. In addition, a reversible wettability‐switching surface has been fabricated to capture or repel gas bubbles in water by selective switching between underwater superaerophobicity and aerophilicity .…”

Patterned Slippery Surface for Bubble Directional Transportation and Collection Fabricated via a Facile Method

“…The manipulation of underwater bubbles is significant in a fluid system due to its large-scale applications, such as electrocatalytic gas evolution reactions, wastewater remediation, and solar energy harvesting [1][2][3][4][5][6][7][8][9][10][11]. Meanwhile, the bubbles play an important role in nature.…”