Abstract
Femtosecond (FS) laser-induced surface structuring is a robust, maskless, non-contact, and single-step process for producing micro- and nanoscale structures on a material’s surface, which remarkably alters the optical, chemical, wetting, and tribological properties of that material. Wettability control, in particular, is of high significance in various applications, including self-cleaning, anti-fouling, anti-icing, anti-corrosion, and, recently, oil–water separation. Due to growing energy demands and rapid industrialization, oil spill accidents and organic industrial discharges frequently take place. This poses an imminent threat to the environment and has adverse effects on the economy and the ecosystem. Oil–water separation and oil waste management require mechanically robust, durable, low-cost, and highly efficient oil–water manipulation systems. To address this challenge superhydrophobic–superoleophilic and superhydrophilic–underwater superoleophobic membrane filters have shown promising results. However, the recyclability and durability issues of such filters are limiting factors in their industrial application, as well as in their use in oil spill accidents. In this article, we review and discuss the recent progress in the application of FS laser surface structuring in producing durable and robust oil–water separation membrane filters. The wide variety of surface structures produced by FS laser nano- and micromachining are initially presented here, while the excellent wetting characteristics shown by specific femtosecond-induced structures are demonstrated. Subsequently, the working principles of oil–water separation membranes are elaborated, and the most recent advances in the topic are analyzed and discussed.
Highlights
Surface structuring using femtosecond (FS) pulses gives rise to spatially resolved micro/nanometer-sized features that are attributed to the reduced thermal and mechanical effects upon the ultrafast laser–material interaction [1,2]
Considering that wetting properties are highly dependent on the shape, size, and surface structures, the polarization control of Laser-induced surface ripples (LISR) should be a useful tool to realize an ensemble orientation of the surface structures, the polarization control of LISR should be a useful tool to of complex morphologies, facilitating the elegant tuning of the wettability of materials used for realize an ensemble of complex morphologies, facilitating the elegant tuning of the wettability of oil–water separation
In the extreme case of a superhydrophilic–underwater superoleophobic surface (Figure 6f), the droplet volume is adsorbed by the surface structures in air, but when an oil droplet is placed on the surface while it is immersed in water, it exhibits a high contact angle for oil
Summary
Surface structuring using femtosecond (FS) pulses gives rise to spatially resolved micro/nanometer-sized features that are attributed to the reduced thermal and mechanical effects upon the ultrafast laser–material interaction [1,2] It is a novel technique for precise control of a wide range of properties on virtually any type of material, including optical, mechanical, chemical, wetting, biological, and tribological properties [3]. With to the energy transfer from the electrons to the lattice depends on the electron–phonon coupling constant; laser-induced surface structures, the electron–phonon interaction is a key factor in understanding the this constant, e.g., inthe metals, the faster the electron-to-lattice transfer occurs theirhigher formation. The energy accumulation material’s and,e.g., the hydrodynamics of electron–phonon coupling constant; on thethehigher this surface constant, in metals, the faster the the molten pool leading to laser-induced self-assembled structures under non-ablation conditions [35]. Apart from the complex, Self-Organized patterned surfaces attained by FS Structures laser micromachining
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