Study On Dynamic Control Of Underwater Bubble Based On Laser Processing

In recent years,laser processing technology has been widely used in precision drilling,precision cutting,micro-nano machining and other fields due to its advantages of high precision and short processing time.The surface wettability can be controlled efficiently and accurately by laser processing to construct ideal microstructure on the surface of materials.Based on the laser processing technology,this paper studies a series of methods to control the underwater bubble,which provides a new perspective for the advanced material design in the fields of ultrahigh speed bubble capture,directional bubbles transport,collection and gas-liquid separation.The full text mainly includes the following parts:?1?The dual UV/thermal-responsive zinc foil with conical hole array were prepared by nanosecond laser micro-drilling.The diameter of micropores on the top surface and the bottom surface were 141?m and 60?m respectively;Once the conical hole array zinc foil is heated,its top surface will show superhydrophobic,while bottom surface remains hydrophilic.This kind of material with asymmetric wettability is vividly called"Janus".Based on the wetting gradient characteristics of Janus zinc foil,we have successfully captured underwater bubbles;Subsequently,after being irradiated for 10hours under the UV LED,the upper surface of Janus zinc foil recovered from superhydrophobic to hydrophilic.We use this kind of double-faced hydrophilic zinc foil to repel underwater bubbles.Based on the dual UV/thermal-responsive characteristics of zinc foil,the reversible switching between Janus zinc foil and double-faced hydrophilic zinc foil can be realized quickly,so as to capture and repel the underwater bubbles.This method of combining nanosecond laser drilling and external stimulation has many advantages:1.Nanosecond laser processing technology is not limited by materials,it can accurately process according to the complex patterns drawn in the control system,so it is more flexible to use 2.Nanosecond laser has high processing efficiency?it only takes 20 minutes to prepare 6x6mm conical hole array?3.In the process of wettability modification,only heat and ultraviolet light are used as external stimulus without additional chemical reagent,which will be safer and more environmentally friendly.?2?In this paper,we used femtosecond laser line by line scanning method to prepare the rice-leaf-like groove structure on the surface of PDMS,and the solid/liquid mixed paraffin?SLMP?was uniformly spun on the surface of PDMS by hot spin coating process.Subsequently,the solid/liquid mixed paraffin injected surface?SLMP-IS?was used to study the anisotropic sliding of underwater bubbles.The results show that femtosecond laser pulse power and thermal-spin-coating speed are important factors affecting the surface anisotropy.Through quantitative analysis,we have obtained the most ideal SLMP-IS,which has a bubble sliding angle of 20°parallel to the groove(SA_//)and 90°vertical to the groove?SA_??.The obvious anisotropy makes the bubble slide on the 45°inclined surface directionally.In addition,the durability test of SLMP in water was also carried out.Compared with the traditional liquid lubricant,SLMP has more excellent stability and durability.