Design And Fabrication Of Superhydrophobic Surfaces Based On Diffusion Bonding Multi-layer Dissimilar Metal Foils

Superhydrophobic surfaces widely exist in nature due to their water repellency characteristic.They are also widely applied in the human production and life such as corrosion resistance,anti-fogging,anti-icing,water/oil separation,directional liquid transmission,water collection,bubble collection,and microfluidics by bionics.It is difficult to build micro structures precisely on metal substrates by the existing methods.In order to solve this problem,we introduced a novel method based on diffusion bonding dissimilar metal foils.Superhydrophobic surfaces with precisely controllable micro structures could be obtained after carrying out chemical corrosion,nanostructure growth,and modification progresses.Hundreds of copper foils and iron foils with different thickness were stacked alternatively and diffusion bonded.After that,the iron on the interface of joints were corroded by chemicals,and the one-dimensional micro structure were fabricated.The effect of corrosives and corrosion time on the depth of grooves were investigated.It is indicated that the obtained surfaces corroded by hydrochloric acid and sulfuric acid were uneven;the obtained surfaces corroded by perchloric acid were even which meant the micro structure could be fabricated precisely.The depths of grooves on surfaces with different ratios of the copper width to the iron width were different when the corrosion time was same.The depth to width ratio of grooves on a surface was approximately proportional to corrosion time.CuO nanoslices were grown on the copper bulges on one-dimensional surfaces after the as-corroded samples were immersed in the solution of 0.12 mol/L K2S2O8 and 3.2 mol/L NaOH at 65 oC for 15 min.The multi-hierarchy structures were fabricated,and the roughness of the surface was improved greatly.After immersed in the ethanol solution of 1-dodecanethiol(0.01 mol/L)at room temperature for 2 days,the as-obtained surfaces showed superhydrophobicities.The effect of modification time,depth to width ratios of grooves,and ratios of copper bulge widths to iron groove width on the contact angles and sliding angles on the as-obtained surfaces were investigated.The surface with the groove depth to width ratio of 0.75 and the ratio of bugle width to groove width of 0.2 shows the best superhydrophobicity.The mechanism of the effect of the micro-structure on surface superhydrophobicities were analyzed.When the groove depth to width ratio was 0.15,the water drop on the superhydrophobic one-dimensional surface was in Wenzel state,when the groove depth to width ratio was beyond 0.3,the water drop on the superhydrophobic one-dimensional surface was in Cassie state.A magnetic control microdrop releasing system based on the as-obtained superhydrophobic one-dimensional surface was built successfully.The magnetic microdrop was in different contact states after the magnetic fields in different directional were applied.