Superhydrophobic surfaces have important applications in generating anti-icing properties, preventing corrosion, producing anti-biofouling characteristics, and microfluidic devices. One of the most commonly used materials to make superhydrophobic surfaces is poly(dimethylsiloxane) (PDMS). Various techniques, including spin-coating, dip-coating, spray coating, surface etching, and laser-textured mold methods, have been used to make superhydrophobic surfaces. However, all these methods require several steps, the usage of multiple chemicals, and/or surface modifications. In this paper, a one-step, low-cost method to induce superhydrophobicity is described. This was done by the pulsed laser deposition of laser-ablated PDMS micro/ nanoparticles, and the method applies to a variety of surfaces. This technique has been demonstrated on three important classes of material�glass, poly(methyl methacrylate) (PMMA), and aluminum. Water contact angles of greater than 150°and roll-off angles of less than 3°were obtained. Optical transmission value of as high as 90% was obtained on glass or PMMA coated with laser-ablated PDMS micro/nanoparticles. Furthermore, this method can also be used to make micron-scale patterned superhydrophobic PDMS surfaces. This would have potential applications in microfluidic microchannels and other optical devices.
Surface microtexturing improves coating adhesion strength due to increased surface area and mechanical interlocking. Grit blasting and laser processing are two common methods used for surface microtexturing. Laser microtexturing offers distinct advantages over grit-blasting as it improves interface quality, provides a grit-particle-free surface, optimized processing time, and greater control over the surface roughness. This paper reports a full area method of laser microtexturing of Al 7075 alloy using a nanosecond pulsed laser to generate a large increase in surface area. This method involves a laser-induced thermo-mechanical process where tightly packed pillar-like surface features were formed due to the surface melting and re-solidi cation of materials combined with some ablation. The morphology of the microtexture was controlled by varying the laser processing parameters. Thereafter, the laser microtextured surface was coated with metallic coatings using thermal spray. Our method is superior to the currently used laser ablation-based microtexturing method. The surface morphology, composition, and adhesion strength results are presented. The tensile adhesive strength of the thermally sprayed metallic CoNiCrAlY coating was measured, and an improvement of over 17% in the coating adhesion strength was observed for a 5 µm deep microtexture compared to that of grit-blasted samples. This is the highest reported adhesion strength for thermally sprayed bond coating.
Surface microtexturing improves coating adhesion strength due to increased surface area and mechanical interlocking. Grit blasting and laser processing are two common methods used for surface microtexturing. Laser microtexturing offers distinct advantages over grit-blasting as it improves interface quality, provides a grit-particle-free surface, optimized processing time, and greater control over the surface roughness. This paper reports a full area method of laser microtexturing of Al 7075 alloy using a nanosecond pulsed laser to generate a large increase in surface area. This method involves a laser-induced thermo-mechanical process where tightly packed pillar-like surface features were formed due to the surface melting and re-solidification of materials combined with some ablation. The morphology of the microtexture was controlled by varying the laser processing parameters. Thereafter, the laser microtextured surface was coated with metallic coatings using thermal spray. Our method is superior to the currently used laser ablation-based microtexturing method. The surface morphology, composition, and adhesion strength results are presented. The tensile adhesive strength of the thermally sprayed metallic CoNiCrAlY coating was measured, and an improvement of over 17% in the coating adhesion strength was observed for a 5 µm deep microtexture compared to that of grit-blasted samples. This is the highest reported adhesion strength for thermally sprayed bond coating.
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