Controlling the Adhesion of Superhydrophobic Surfaces Using Electrolyte Jet Machining Techniques

Abstract

Patterns with controllable adhesion on superhydrophobic areas have various biomedical and chemical applications. Electrolyte jet machining technique (EJM), an electrochemical machining method, was firstly exploited in constructing dimples with various profiles on the superhydrophobic Al alloy surface using different processing parameters. Sliding angles of water droplets on those dimples firstly increased and then stabilized at a certain value with the increase of the processing time or the applied voltages of the EJM, indicating that surfaces with different adhesion force could be obtained by regulating the processing parameters. The contact angle hysteresis and the adhesion force that restricts the droplet from sliding off were investigated through experiments. The results show that the adhesion force could be well described using the classical Furmidge equation. On account of this controllable adhesion force, water droplets could either be firmly pinned to the surface, forming various patterns or slide off at designed tilting angles at specified positions on a superhydrophobic surface. Such dimples on superhydrophopbic surfaces can be applied in water harvesting, biochemical analysis and lab-on-chip devices.

Bioinspired Special Wettability Surfaces: From Fundamental Research to Water Harvesting Applications

“…They made use of electrochemical etching to fabricate micro‐nano structures on the aluminum alloy substrate, microdimples became smoother and the boundary between the edge of dimples and superhydrophobic area was more separated with the processing time or increased voltages. Microdimples with different roughness and dimensions were obtained via EJM by regulating the processing time and voltage on the aluminum alloy substrate and the substrate exhibited controllable levels of adhesion after surface modification of stearic acid …”

“…Apart from the essential process of fabrication of materials for water‐harvesting, multicreature‐bionics, three‐dimensional materials and optimal design should be taken into consideration in further research. Recently, based on theories stemmed from Namib desert beetles, cacti, and pitcher plants, Park et al presented a conceptually different design approach to fabricate an integrated and optimized surface . The surface synergistically combined these water‐harvesting processes of three creatures, viz.…”

Bioinspired Superhydrophobic Surface Constructed from Hydrophilic Building Blocks: A Case Study of Core–Shell Polypyrrole-Coated Copper Nanoneedles

“…The existence of the transition indicates that the superhydrophobic state observed on the PPy-CuND-PET surface is meta-stable. However, the capability of simultaneously maintaining a high water contact angle and high adhesion makes the PPy-CuND-PET surface quite attractive for the manipulation of microdroplets, which is important for biological reactions, microfluidic devices, traced analysis, and in situ detection [21][22][23]. These findings may help to develop a superhydrophobic surface based on reentrant structures that omits fluorinated coatings and design a superhydrophobic surface with tunable adhesion and particle retention.…”

Super-antiwetting with High Adhension Property of Pitcher Plant

“…It is generally recognized that the adhesive force of superantiwetting surface is related to the surface roughness and morphology [15][16][17]: rough surface morphology results in low adhesion and superhydrophobicity, while smoother surfaces are adhesively hydrophobic. In general, the one with low adhesion has nanometer scale projection [18,19] or rough porous textures [20,21] on the microstructures on the surface, lowering the surface tension.…”