Fabrication Of Super-Hydrophobic Biomimetic Structures On Metal Surface By Femtosecond Laser Based On Spatial Light Modulation Technology

The super-hydrophobic biomimetic surface has many outstanding properties,such as self-cleaning,anti-corrosion,effective prevention of microbial adhesion and anti-icing properties,so it has very important research value and wide application prospects.Biomimetics mainly includes surface morphology and specific functions.Femtosecond laser processing technology has the characteristics of wide material universality,high processing accuracy,and strong controllability.It has outstanding advantages in the preparation and regulation of special wetting surfaces.The laser direct writing method is a commonly used processing method of biomimetic structures,but its single exposure point is simple,in the case of the process of complex and precise patterns requires point-by-point scanning,which efficiency is low.The femtosecond laser spatiotemporal interference method based on Liquid Crystal on Silicon-Spatial Light Modulator(LCo S SLM)can modulate the spatial light field of single exposure more flexibly,and any designed pattern can be directly obtained in single exposure,which significantly improves the processing speed.It is very conducive to processing irregular structures and imitate the microscopic shape of organisms in nature.In this paper,the femtosecond laser spatiotemporal interference method based on spatial light modulator is developed.By changing the 800 nm femtosecond laser fluence and the cumulative pulse number,different biomimetic structures were prepared on two kinds of metal surfaces with high efficiency and quality.The wettability of the structures fabricated with different laser parameters were also analyzed.The main research results are as follows:1.In this paper,the principle of the spatiotemporal interferometric femtosecond laser device is introduced and simulated,and the flexibility of the device to control the two-dimensional light field is demonstrated.Using this method,two-scale biomimetic shark skin surface micro-nano structures were processed on316 mirror stainless steel.When the laser fluence is 1.37 J/cm2 and the cumulative pulse number is 30 ~ 40,the wettability of the material surface is changed from hydrophilic(contact angle is 88°)to super-hydrophobic and the water contact angle is as high as 165°.The formation reason of super-hydrophobic surface is analyzed from the change of element content and the wettability model.2.Based on this technology,the biomimetic structure of butterfly wing scales was prepared on the surface of titanium alloy(Ti-6Al-4V).The wettability of the material surface changes from hydrophilic(contact angle is 61°)to hydrophobic.When the laser fluence is 1.46 J/cm2 and the cumulative pulse number is 50,the processed surface are composited with micron-level papillary structures and periodic nano-stripes attached,the maximum contact angle is 134°,which is an increase of 73° compared to the surface of the unprocessed titanium alloy.In this study,a flexible and efficient femtosecond laser spatiotemporal interference method is developed to obtain a stable hydrophobic surface on the titanium alloy material.It is expected that the material will be used in aerospace to achieve the ice-relief function and provide a new idea for the preparation of biomimetic structures.