Fundamental Research On Preparation Of Superhydrophobic Acoustic Metasurface By Laser Etching Aluminum Alloy

Acoustic metasurface is a man-made composite structure with special acoustic properties that many materials do not have.The size of the structure is much smaller than the wavelength and it can control the low-frequency acoustic waves with small-size structure.With the development of ocean resources by humans,more attention has been paid to the application of underwater acoustic metasurfaces,such as imaging,underwater detection,and acoustic stealth.Currently,there are few researches on the working mechanism and influencing factors of superhydrophobic metasurfaces.In this paper,the underwater acoustic metasurface is prepared with aluminum alloy plate as the substrate by laser etching technology and its underwater acoustic characteristics are tested on the underwater acoustic test platform.The research work of this paper is as follows:1.Designed a structure of laser textured covering cavity.The texturized superhydrophobic surface is prepared by a simple laser etching method,and the superhydrophobic overlay plate prepared by laser etching is seamlessly connected with the aluminum alloy cavity plate to prepare the laser textured overlay cavity structured acoustic surface(LTOCS).The underwater acoustic tests showed that LOCS has a good sound insulation ability in the designed frequency range(50 k Hz-60 k Hz).The underwater sound transmission coefficient is reduced by up to 81%.Its working mechanism is the Minnaert resonance of the micro-surface bubbles and the absorption and reflection of the Schroeder cavity structure.2.The periodic structure of the superhydrophobic acoustic surface was obtained by etching the periodic grid-like grooves on the surface of aluminum alloy with the scanning distance of 50?m,90?m and 130?m,respectively,using an infrared nanosecond laser.The contact angles of three superhydrophobic surfaces with different scanning distances were156.2 °,153.6 ° and 151.3 °,respectively.The outcomes of acoustic test showed that with the increase of the scanning distance and the immersion time in the water,the underwater acoustic transmission coefficient of the sample increases,the absorption coefficient decreases,and the acoustic characteristics become worse.By changing the laser scanning distance of the surface,the purpose of adjusting the acoustic performance of the underwater acoustic metasurface can be achieved.This research shows the potential of laser-textured superhydrophobic surfaces in underwater acoustic applications,and provides technical solutions for effective control of underwater low-frequency acoustic waves,which can be used to suppress underwater noise propagation,acoustic stealth,underwater detection,etc.