Dynamic Wetting Behavior And Regulation Mechanism Of Metal-based Bionic Smart Surface

“It is not the strongest of the species that survive,but the one most responsive to change”.During the evolution of hundreds of millions of years,in order to meet the needs of survival and development,some biological surfaces have evolved unique wettability.In recent years,biomimetic materials with special wettability have gradually become one of the research hot-spots.Many breakthrough scientific achievements have greatly promoted the development of this field.However,with the deepening of research,people are no longer satisfied with simply imitating nature.Because of its unique advantages,smart biomimetic materials that can change surface wettability have received increasing attention.So far,many researches on the reversibly switchable wettability in the field of polymer materials have made promising progress.As one of the materials widely used in engineering,relatively few studies have been conducted on the switchable wettability of the metal surface,which has limited the development of smart wettability materials to a certain extent.In addition,due to the high processing cost,complex preparation method,poor stability and durability,the wide application of the material is limited.Based on the above analysis,in this paper,the bionic metal surface is designed and prepared by referring to the typical biology with special wettability in nature and combining with the research trend of smart wettability surface.Through dip coating,poly-electrolyte deposition,laser processing and chemical modification,smart surfaces with switchable wettability can be prepared on relatively stable metal surfaces such as titanium and copper.Furthermore,we analyzed and summarized the internal mechanism of switchable wettability,and tested the stability and durability of the surface.The as-prepared smart bionic surface can be used to solve practical engineering problems,such as oil-water separation,droplet/fluid manipulation and anti-corrosion.The main conclusions can be summarized as follows:(1)A biomimetic Ti O2 titanium mesh(BTTM)with switchable wettability was successfully prepared by a simple dip coating method.After UV irradiation or heating,the wettability of the surface can change reversibly between underwater superoleophilicity and underwater superoleophobicity.After 12 hours immersion in high concentration of acid,alkali,or salt solution,the wettability of BTTM has almost no change,showing good chemical stability.In addition,BTTM also has self-healing ability,self-recovery anti-oil-fouling property and self-cleaning behavior,which can resist oil pollution and improve recyclability.This study provides a simple and efficient strategy to fabricate a stable smart surface for controllable treatment of corrosive oily wastewater.(2)By laser processing and alternating deposition of polyelectrolytes on commercial copper surfaces,we have obtained superhydrophobic platforms with high adhesion and ion-responsive wettability.When the external counter ion changes,the wettability of the as-prepared bionic platform can be switched between superhydrophobicity and superhydrophilicity.In addition,the bionic platform has good physical and chemical stability.Wetting model shows typical Cassie impregnating wetting state.Based on the above special surface wettability,the bionic platform can not only be used as a "manipulator" to transfer the droplets,but also as a rewritable droplet storage platform to achieve selective storage or patterned arrangement.This research will help the development of droplet transfer,functional storage and metal microfluidic platforms.(3)By laser processing,chemical etching and mixed thiols modification,we have obtained a superhydrophobic bionic copper surface with p H-responsive wettability.Due to the protonation and ionization of carboxyl groups at different p H values,the wettability of the bionic surface can be reversibly changed from superhydrophobic to superhydrophilic.By covering or removing the ink,we can achieve the transition from high adhesion to low adhesion.Specifically,when the diameter of the ink dot is 0.6mm,the contact angle of the water droplet(5 ?L)is 152 ± 1.5 °,and it shows a high adhesion state(SA = 90°).This smart bionic platform can be used to store droplets,transfer droplets,or as a droplet micro-reaction platform.Electrochemical test results show that the as-prepared surface has good corrosion resistance.This research realizes the simultaneous control of contact angle and adhesion of droplets,which is helpful to promote the development of the droplet reaction platform,and provides a new idea for the anti-corrosion of copper.(4)Based on previous studies,inspired by natural reed leaves and lotus leaves,combined with reversible switching wettability and rational design of two bionic structure layouts,multifunctional dual-bionic metal platforms were successfully prepared.For neutral(p H = 7)water droplets and underwater(p H = 13)oil droplets,the "reed leaf" and "lotus leaf" areas of the bionic metal platform have anisotropic wettability and isotropic wettability,respectively.The difference between the energy barrier and the three-phase contact line makes the bionic "reed leaf" have anisotropic wettability.The dual bionic metal platform can realize the manipulation of water/oil droplets and fluids,which will promote the research of integrated bionic functional surfaces and provide new strategies for designing multi-purpose and multi-functional metal microfluidic platforms.