Construction Of The Bionic-structured Superhydrophobic Surface And Antimicrobial Application

The phenomenon of bio-adhesion and aggregation on materials surface has brought great harm to human life and production,causing great impact on medical,food,and shipping industries.The surface wettability,electric charge,surface energy,and structural morphology all affect the interaction between the materials and the organisms.Moreover,these factors are not mutually independent,but influence each other and jointly determine the bio-adhesion behavior of materials surface.From the perspective of research ideas,methods and results,bionic surface is undoubtedly effective and excellent solutions.After hundreds of millions of years of evolution,animals and plants in the natural world have possessed perfect structures with excellent performance,enabling them to achieve the coordination and unity among structures,materials,and functions.“The lotus does not stain the mud,” and the fish are still able to maintain their own cleanliness in oil-contaminated seas.These miraculous natural phenomena also confirm that the surface with special infiltration properties can achieve the effect of anti-bioadhesion.Therefore,to prepare anti-adhesion surfaces from the perspective of bionics,taking the special micro/nano structure,chemical composition and specific chemical organisms of surfaces in nature as templates is an effective solution for the current and even long-term time.From the perspective of coupled bionics,this paper systematically studies and analyzes the typical wettability leaves,establishes a bionic mathematical model,reveals the wetting behavior mechanism and dynamic behavior of typical plant leaf surfaces,and proposes the factor coupling mechanism of structures,forms,and compositions.Three typical superhydrophobic plants,including lotus leaf,rose petal and calendula officinalis,were selected for the study.By observing the surface microscopic structure and testing the wettability,the results show that the surface superhydrophobic function is achieved by the multi-factor coupling effects,including structure,morphology,and materials;the surface microstructure exhibits a micro-nano/micro-bimodal or multi-stage structure;the surface morphology is mostly convex hull and the surface has a wax layer.Meanwhile,the principle of multi-level structure design of bionic surface is established,which provides a theoretical basis for the establishment of bionic model and surface design.Based on the basic biology research,stainless steel is selected as the base material to prepare a bionic multifunctional superhydrophobic surface in this paper,because it is widely used in many fields.(1)Preparing biomimetic superhydrophobic antimicrobial surfaces on stainless steel substrates by laser processing combined with chemical modification.Inspired by the special micro/nanostructures of organisms and the bio-adhesion of marine mussels,the low surface energy chemical components were successfully anchored to the patterned stainless-steel substrate by laser interference patterning and in-situ graft polymerization,thereby obtaining a superhydrophobic surface with self-cleaning properties.A series of bacterial experiments,including agar plate method,fluorescence microscope observation and milk immersion method,confirmed that the prepared biomimetic superhydrophobic surfaces have certain antibacterial properties.In addition,the relevant experiments also showed that the prepared sample has good thermal stability,mechanical stability and long-term stability,which is conducive to expanding the application of stainless steel.(2)Preparing biomimetic anisotropic superhydrophobic surfaces by laser processing.Combining the unique microscopic surface structure and characteristics of lotus leaf,butterfly wing and rice leaf,three patterned surfaces with single or mixed morphological structure were designed and fabricated by optimizing laser processing parameters.Ultimately,anisotropic superhydrophobic surfaces were prepared on stainless steel substrates by combining patterned surfaces and modification treatment.Moreover,the theoretical values calculated from the molecular thermodynamic equation are consistent with the actual measurement results.In conclusion,the continuity of the three-phase contact lines in different directions and the energy difference when the droplets are stable are the main reasons for the anisotropic wetting of the surface.(3)Simulating the mechanism of the formation of superhydrophobic membranes by molecular dynamics.The molecular dynamics simulation and quantum chemistry are used to analyze the formation process of superhydrophobic surface,which provides a theoretical basis for the superhydrophobic surface formation mechanism.At the same time,the molecular dynamics simulation of the adsorption process of water molecules on the surface of stainless steel and superhydrophobic membranes were performed.The results showed that the droplets spread rapidly on the surface of stainless steel,but the original shape was still maintained on the superhydrophobic surface.The results are consistent with the experimental results,demonstrating that the unity of theory and practice was achieved,verifing the functional mechanism of superhydrophobic membranes via molecular dynamics theory.(4)Preparing biomimetic superhydrophobic antibacterial stainless-steel mesh surfaces by electrodeposition.The silver nanoparticles were deposited on the stainless-steel mesh by the double potential step method,and then the super-hydrophobic stainless-steel mesh surface with self-cleaning properties was successfully obtained through surface modification.The growth process and influencing factors of silver nanoparticles during electrodeposition were analyzed in detail,including the concentration of the complexing agent sodium citrate,silver nitrate concentration,nucleation potential,nucleation time and growth time.The antibacterial properties of the surface of the stainless steel containing the silver coating were comparatively analyzed by a static inhibition zone test.The surface of the stainless steel containing the silver coating before and after the modification was respectively placed in the broth under different culture conditions,and the bacteria were respectively stuck under a static culture in a constant temperature incubator at 37°C and a dynamic culture with a rotation speed of 50 rpm and a culturing temperature of 37°C.Attached to the situation,it was concluded that the superhydrophobic surface was conducive to the reduction of bacterial adhesion,whereas static culture had a significant effect on the reduction of bacteria.