Foundmental Research Of Superhydrophobicity Underwater Acoustic Metasurfaces By Laser Ablation

The acoustic metasurfaces have unique physical properties such as planar and ultra-thin,and the ability of flexible regulation of acoustic waves.It has an important application prospect in many acoustic fields such as noise reduction and vibration isolation,stealth technology and noncontact control of objects.Acoustic metasurfaces with superhydrophobic properties have not yet been investigated.Based on the laser etching technique,a cross micro-groove superhydrophobic acoustic metasurface was designed and fabricated,and its underwater acoustic propagation performance was tested by a self-built platform.The main research work includes:1.Cross groove is ablated by ultraviolet laser in glass fiber reinforced plastics(GFRP),then trimethoxysilane is spin-coated and heat-treated by thermostat at 170 °C for 30 min to get superhydrophobic structure of acoustic absorption metasurface.The test results show that the absorption coefficient of acoustic waves on the GFRP superhydrophobic surface is above 88% in the frequency range of 50 kHz to 250 kHz,and the physical mechanism is mainly the multi-interface scattering effect induced by the air layer between the water and the superhydrophobic microstructure.2.A resonant membrane acoustic metasurface composed of a thin film fixed on an aluminum plate and a copper block attached to the surface is designed.After laser ablation using different spacing parameter,copper surfaces with different superhydrophobic/hydrophilic properties were obtained by chemical modification,resulting in different adhesion surfaces.The results show that the higher the adhesion of the copper surface,the higher the transmission coefficient of the resonant structure.By changing the surface wettability of the copper block,further modulation of its underwater oscillation mode can be realized.The research results of this paper demonstrate the potential application of graphically superhydrophobic acoustic metasurfaces by laser in the field of underwater acoustics and provide a new technical approach for the engineering application of underwater acoustic metamaterials.