Research On The Construction Of Bionic Functional Surface And Antifouling Mechanism Based On The Harmonic Motion Antifouling Strategy

Marine microorganisms adhere to the surface of the solid wall and form biofouling,which brings great harm to ships and marine facilities.The harm caused by biofouling is mainly reflected in the following three aspects:(1)Increased ship resistance and fuel consumption;(2)Accelerated the corrosion of ships and pipeline transportation shells;(3)Increase the number of repairs and raise maintenance costs.In the early days,people reduced the adhesion of fouling organisms by adding toxic components to antifouling coatings.With the ban on toxic antifouling agents by environmental laws and regulations,research and development of new environmentally friendly antifouling technologies is imminent.Coral is a kind of fixed organism that grows in the marine environment for a long time.It cannot use water to wash by swimming to reduce the adhesion of fouling organisms,but the surface is very clean.The study found that coral antifouling strategies mainly include the release of natural antifouling ingredients,fouling-release antifouling surface strategies,moulting antifouling strategies,fluorescent antifouling strategies,and "harmonic motion" antifouling strategies.Coral's elastic skin and tentacles respond to the periodic excitation of waves through elastic deformation of a certain frequency and amplitude,which can effectively prevent the formation of microbial membranes.Based on the Sarcophyton trocheliophorum tentacle "harmonic motion" antifouling strategy,this paper will carry out a systematic study on the design,preparation and antifouling mechanism of the tentacle "harmonic motion" antifouling bionic functional surface(hereinafter referred to as the bionic functional surface).Through Sarcophyton trocheliophorum's "harmonic motion" regular biological observation experiment,it is found that a single fully extended tentacles are concentrated between 7 mm and 13 mm in height,which are cone-shaped,randomly distributed and closely spaced.The tentacles are excited by the fluid medium and achieve a "harmonic motion" response by swinging and forming an unstable surface.For the attachments close to the surface,it actively sweeps and bounces to prevent it from adhering to the surface.Based on the above-mentioned "harmonic motion" anti-fouling strategy,the design of the bionic functional surface is as follows: Use room temperature vulcanized silicone rubber(RTV-2)with 0.36 wt% graphene as the base material to imitate the elastic surface of Sarcophyton trocheliophorum.It has a tentacle-like conical structure with a top diameter of 0.8 mm and a bottom diameter of 1 mm.The top and bottom edges of the tentacles are respectively provided with arc chamfers to simulate the semi-circular arc at the top of the coral tentacles and the connection between the bottom and the epidermis.Three parameters are set for tentacle length and spacing,which are 7 mm,10 mm,13 mm in length,and 2 mm,2.5 mm,3 mm in spacing.The bionic functional surface is prepared as follows: The RTV-2/0.36 wt% base material is prepared by the mechanical blending method.Design and manufacture special modeling molds and fixed molds with the mirror structure of the bionic functional surface,and use the template method to prepare bionic functional surfaces of different sizes and structures.Through the mechanical properties,weight loss rate/water absorption rate,roughness,wettability test and characterization,it is found that the base material for preparing the bionic functional surface has a stable weight loss rate/water absorption rate(less than1%),a low elastic modulus(about 0.56 MPa)and roughness,and hydrophobicity.These characteristics provide favorable conditions for its antifouling performance.Through the dynamic/static test,the antifouling performance comparison test is carried out on the bionic functional surface and the 0.36 wt% silicone rubber graphene composite film without a tentacle structure(hereinafter referred to as the graphene composite film).(1)In the static test,the amount of bacteria attached to the bionic functional surface is almost the same as the graphene composite film,indicating that the anti-fouling performance of the two is equivalent under completely static conditions;(2)Dynamic test,select two kinds of self-designed test equipment for test.(1)Simulating ocean wave equipment-"wave type" anti-fouling test.The analysis shows that the antifouling effect of the bionic functional surface is better than the graphene composite film,and the faster swing frequency the better antifouling effect.Prove the "harmonic motion" effect of the tentacles can prevent the adhesion of bacteria.At the same time,it is concluded that the length of the tentacles and the swing frequency are the main factors that affect the anti-fouling performance of the bionic functional surface under the action of water flow fluctuations.Select the best anti-fouling combination with a swing frequency of 1 Hz and a tentacle length of 13 mm.Speeding up the swing frequency can make full use of the "harmonic motion" for the tentacles.After observation,it is found that the long tentacles structure under the action of the water current fluctuations,the top of the tentacles will form a second tremor with the water flow,which can double removal of bacterial adhesion.(2)Dynamic rotating scouring equipment-"rotating" anti-fouling test.It is also proved that the antifouling performance of the bionic functional surface is better than that of the graphene composite film,and the bionic functional surface with 13 mm tentacles and 2 mm spacing has the best antifouling effect.The long tentacle structure can be bent to the greatest extent under the action of water flow and superimposed on the surface of the back layer to form an anti-fouling protective layer.At the same time,the tentacle shakes and produces "harmonic motion" anti-fouling with the help of the water flow.The denser tentacles can fill in the gaps on the bionic functional surface,maximizing the antifouling effect of the tentacles "harmonic motion".Through the EDEM-FLUENT coupling simulation,carry out the research on the antifouling mechanism of the "harmonic motion" antifouling bionic functional surface.The tentacle structure(biomimetic functional surface)and flat structure(graphene composite film)are selected as the experimental control group.The test results show that the amount of bacteria attached to the tentacle structure is much lower than that of the flat structure,and it also shows that the faster flow field,the lower amount of bacteria attached.The sedimentation of bacterial particles to the tentacle structure only occurs in the area near the tentacles,and the time for the bacterial particles to settle is relatively short.The flat structure will leave a larger and longer sedimentation area and sedimentation time for the bacterial particles.The test results prove that the tentacle structure can effectively reduce the adhesion of the bacterial particles.The experimental results of this paper provide new ideas for the development of environmentally friendly antifouling bionic functional surface and new concepts for antifouling technology of static ships,underwater equipment and facilities.