Mask Micromachining Of Superhydrophobic Cylindrical Array Structures On Metal Substrates

Superhydrophobic surface has a set of excellent properties such as self-cleaning, anti-corrosion, drag reduction, droplets’ directionally motion and nondestructive transfer, antifogging, anti-icing and so on. Therefore, superhydrophobic surface has a wide application prospect in industrial manufacture, medical treatment and national defense fields.In this paper, mask electrochemical method and mask chemical method were proposed to fabricate super hydrophobic surface by maching small cylindrical array structure on Al and Cu substrate in view of the limited material requirement, low possibility for realizing industrialisation production and higher cost of the existing metal matrix super hydrophobic surface preparation methods. Additionally, the effect laws of process parameter on cylindrical array structures size and cylindrical array structures size on metal surface wettability was explored based on massive experiment results.From the experiments of maching cylindrical array structure by mask electrochemical method, it is found that supersonic vibration could improve the electrochemical etched surface quality effectively,20 s and 240 s were found to be the proper exposure time and developing time for preparing the photoresist mask on aluminum substrate. Also, the diameter of cylinder in array was found to have a decreasing trend, while the interval between cylinder and the height of cylinder were found to have an increasing trend with increasing current density and process time during electrochemical etching process. However, an excessively long process time would cause structural damage of the cylindrical array structures.From the experiments of maching cylindrical array structure by mask chemical method, 20 s and 360 s were found to be the proper exposure time and developing time for preparing the photoresist mask on copper substrate, the diameter of cylinder in array was found to have a decreasing trend, while the interval between cylinder and the height of cylinder were found to have an increasing trend with increasing process time, also, excessively long processing time will cause structural damage.Proper mask size and process parameters were selected to machine cylindrical array microstructures with different size on aluminum and copper substrate based on the noted effect laws of process parameter on cylindrical array structures size. Then the influence rule of cylindrical array structures size on metal surface wettability was explored after modifying the substrate by low surface energy. The experiment results indicate that droplet on copper and aluminum super hydrophobic surface of same size cylindrical array microstructures was in different contact states, the height of cylindrical array was found to be larger on aluminum substrate than copper substrate to realize a Cassie-Baxter contact state. Also, super hydrophobic performance is found to be more obvious when droplet on surface of cylindrical array structure is in a Cassie-Baxter contact state and contact angle increased with decreasing the diameter of cylinder in array and increasing the interval between cylinder, while changed little along the height of cylinder. A superhydrophobic surface with average contact angle of 156.5°as obtained on aluminum substrate under 60 μm (diameter of cylinder in array),100 μm (interval between cylinder) and 40 μm (height of cylinder) respectively, while a superhydrophobic surface with average contact angle of 161.5°as obtained on copper substrate under 60 μm (diameter of cylinder in array),100 μm (interval between cylinder) and 45 μm (height of cylinder) respectively.