Research On Nanosecond Laser Fabrication Of Superhydrophobic Conical Arrays On Metal Substrates

In the past two decades,the superhydrophobic surface inspired by nature has shown good application prospects in the fields of self-cleaning,directional transportation,mist collection,corrosion resistance,fluid drag reduction,liquid pumpless transportation,anti-icing and other fields.Therefore,it has received extensive attention from research scholars.Among them,the superhydrophobic conical column array has the characteristics of enhancing the surface liquid repellency effect,improving the efficiency of oil-water separation,reducing the liquid-solid contact time,and controlling the bounce shape of droplets,so it has received extensive attention.Although there are many methods for processing superhydrophobic conical column arrays,the shortcomings of low efficiency,high cost,and difficulty in large-area processing on a variety of metal materials limit the practical application of these methods.In view of this,this paper proposes a nanosecond processing method with high efficiency,low cost and large-area processing of super-hydrophobic conical column arrays on a variety of metal substrates.First,the nanosecond pulsed laser is used to process the surface of the metal substrate in a single pass to pre-build the micro/nano structure on the top of the superhydrophobic micropillar array;secondly,the nanosecond laser scans multiple times according to the set scanning track to directly process the sub-millimeter conical array;Finally,after being modified by low surface energy materials,a superhydrophobic cone-column array is obtained.Under different laser processing parameters,the size and morphology of the conical arrays processed on metal substrates such as aluminum,titanium,copper,stainless steel,etc.,are studied.At the same time,the influence of the size parameters of the superhydrophobic conical column array on the liquid-solid contact characteristics is explored,and further study the anti-physical friction and anti-chemical corrosion performance of the superhydrophobic micropillar array.The main work is as follows:Systematic laser processing test results show that the height H of the metal array gradually increases with the increase of the laser power P,the number of scans T,and the decrease of the scan speed V,while the sidewall taper does not change significantly.After being modified with fluorosilane(FAS)for low surface energy,the conical arrays of different metal substrates all obtained superhydrophobicity with a contact angle of about 164°and a rolling angle of about 5°.A high-speed camera was used to explore the liquid-solid contact characteristics of the metal conical array,and the influence of the size parameters of the superhydrophobic conical array on the liquid-solid contact time t_contact of the water droplets was studied.The results show that when the Weber number We=16.7,the shortest liquid-solid contact time t_contact of the water droplet can reach 3.3 ms,and the full bounce is achieved without obvious shrinkage.Array gap S=200?m?400?m,array height H>400?m,tip diameter D<800?m,all have good liquid-solid contact characteristics.In addition,the experiment found that the processed oblique conical array can realize the bounce of the droplets in the horizontal direction.Among them,the 30°?45°oblique cone array has the best effect,and the horizontal movement distance of 15?L water droplets can reach about 1.7 mm when the Weber number We=16.7.In addition,through corrosion resistance test,anti-icing test,and friction test,it is verified that the metal array obtained by this processing method has excellent physical strength,chemical corrosion resistance and the anti-icing properties.It has also been practically used in harsh environments.