A Twice Electrochemical-Etching Method to Fabricate Superhydrophobic-Superhydrophilic Patterns for Biomimetic Fog Harvest

Abstract

Superhydrophobic-superhydrophilic patterned surfaces have attracted more and more attention due to their great potential applications in the fog harvest process. In this work, we developed a simple and universal electrochemical-etching method to fabricate the superhydrophobic-superhydrophilic patterned surface on metal superhydrophobic substrates. The anti-electrochemical corrosion property of superhydrophobic substrates and the dependence of electrochemical etching potential on the wettability of the fabricated dimples were investigated on Al samples. Results showed that high etching potential was beneficial for efficiently producing a uniform superhydrophilic dimple. Fabrication of long-term superhydrophilic dimples on the Al superhydrophobic substrate was achieved by combining the masked electrochemical etching and boiling-water immersion methods. A long-term wedge-shaped superhydrophilic dimple array was fabricated on a superhydrophobic surface. The fog harvest test showed that the surface with a wedge-shaped pattern array had high water collection efficiency. Condensing water on the pattern was easy to converge and depart due to the internal Laplace pressure gradient of the liquid and the contact angle hysteresis contrast on the surface. The Furmidge equation was applied to explain the droplet departing mechanism and to control the departing volume. The fabrication technique and research of the fog harvest process may guide the design of new water collection devices.

Superamphiphobic coatings based on liquid-core microcapsules with engineered capsule walls and functionality

“…Such patterned substrates could potentially be beneficial in e.g. fog harvesting devices, microchannel devices, lab-on-chip devices or other droplet manipulation applications 33 – 35 . Also, the motivation for using microcapsules, instead of solid particles, is that the microcapsules could deliver some additional payload that could be beneficial in e.g.…”

Robust Super-Hydrophobic Coating Prepared by Electrochemical Surface Engineering for Corrosion Protection

“…Other researchers also applied electrochemical etching method on aluminum surface. Yang et al reported a two-step electrochemical-etching method combining electrochemical-etching and masking technology to fabricate super-hydrophilic dimple patterns on etched super-hydrophobic Al substrates [81]. The super-hydrophobic layer exhibited high E corr due to the adhesion of the bubbles on the surface and the flat super-hydrophilic dimples can be controlled by switching different etching voltages.…”

A universal method to create surface patterns with extreme wettability on metal substrates

“…Kinoshita et al [29] used a laser plasma-type hyperthermal atom beam facility to achieve superhydrophilic-superhydrophobic micro-nanostrucutures on carbon nanotube (CNT) films. Yang et al [30] fabricated the superhydrophilic-superhydrophobic patterned surface on metal superhydrophobic substrates using a two-step electrochemical-etching method. Combining the masked electrochemical etching and boiling-water immersion methods, they prepared long-term superhydrophilic dimples on the superhydrophobic Al substrate.…”

“…Zhang's group used ink-jet printing technology to make superhydrophilic patterns on the superhydrophobic surface of the desert beetle, showing powerful catchment capability. Yang et al [30] fabricated different superhydrophilic-superhydrophobic patterns on the Al surface by using the two-step electrochemical etching method and studied the effect of different wettability patterns on the fog collection efficiency. However, the effect of the patterned surfaces of different metallic materials on the efficiency of the fog harvesting process is rarely reported.…”